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Antibody Drug Conjugate Development: Keys to Rapid IND Submission and Approval

Antibody drug conjugates (ADCs) are a relatively new type of drug that combines the targeting ability of a biologic with a highly potent cytotoxic agent.

This powerful combination promises to become a game-changer in the fight against cancer—potentially replacing broad spectrum chemotherapies with more specific, less damaging options. At the same time, because ADCs’ cell-killing drug payloads are thousands of times more toxic than conventional treatments, safety concerns are proportionally amplified. That makes gaining regulatory approval for first-in-man studies far more demanding than with a traditional biopharmaceutical.

While it’s natural for pharmaceutical developers to focus on toxicological and pharmacological findings from animal studies, far too often, early stage ADC developers underestimate the importance of their filing’s Chemistry Manufacturing and Controls (CMC) section. This may result in regulatory requests for additional information or unanticipated studies, which can delay or even permanently derail a promising program.

This white paper discusses a pragmatic approach to helping ADC developers ensure IND success. It highlights two main challenges:

  1. Complexity of the ADC molecule
  2. Insufficient CMC data

This publication outlines strategic and analytical approaches that can save time and effort, and help ensure that regulatory requirements for CMC data are satisfied. It suggests that the best way to accelerate the regulatory path to first-in-man studies is to focus the CMC development plan on three areas:

  1. Critical Quality Attributes (CQA)
  2. Frequently overlooked studies
  3. Platform approaches

1.0 Antibody-drug Conjugates and the IND Process
Before human clinical trials can commence in the United States, new drugs must go through a complicated and time-consuming Investigational New Drug (IND) application and approval process. An IND application must demonstrate complete pharmaceutical or biopharmaceutical analyses. In addition to extensive data from animal pharmacology, toxicology studies, clinical protocols and investigator information, it must include detailed Chemistry, Manufacturing and Controls (CMC) information on the manufacturing and stability of the clinical trial material (CTM).[3]

When it comes to clinical studies with ADCs, additional scrutiny of CTM is to be expected. The inherent instability of biologics, together with the level of toxicity associated with an ADC’s small molecule payload have grave implications on patient safety. It is not surprising, then, that CMC data requirements and the level of analytical support needed to support an ADC program are substantially greater than with more traditional therapies.

According to the editors of ADC Review / Journal of Antibody Drug Conjugates, “One of the most critical aspects is to address all the unique issues involved in the submission of an IND completely, correctly, and in a timely fashion…” [2]

Incomplete or incorrect information can result in requests for additional studies, delaying the filing of a successful IND or worse—the financially motivated end to an otherwise promising program. But with a well-planned approach to testing and diverse technical/analytical expertise on your team, ADC developers can avoid these pitfalls and help ensure a seamless path to the clinic.


2.0 Why ADC development is so hard
According to the 2016 Nice Insight CDMO Outsourcing Survey, 57% of companies surveyed said they were developing ADCs, compared to 51% who said they have naked monoclonal antibodies (mAbs) in development.[4][5] Another source states that 182 companies around the world have ADCs in their pipeline.[6] Despite this surge, only four ADCs have been licensed to date. Plenty of examples exist of drugs that showed potential in early pre-clinical stages, but didn’t progress, and were terminated. Many of these failures were due to toxicity or incomplete characterization data.[7][8]

This white paper deals with two of the most common challenges relating to IND approval for ADCs. These are:

  1. The complexity of the ADC molecule itself, which is critical, as analysis of this complex structure informs decisions about its design and manufacture.
  2. Lack of necessary CMC data on the clinical trial Material

2.1 Challenge #1 – The complexity of the ADC molecule
The analytical challenges unique to ADC development are numerous, but chief among them are the complexity and stability of the mAb, the very difficult synthesis and characterization of the small molecule payload (cytotoxic agent) and linker, the chemical linking chemistry, and different conjugations that may be involved. [9][10][13]

Figure 1.0: Schematic showing the complexity and various components of an antibody drug conjugate.

Understanding the structure and behavior of biologically derived molecules–and interpreting analytical findings to inform development decisions—requires a myriad of analytical techniques and experienced biopharmaceutical scientists.[12]

Few Contract Manufacturing Organizations (CMOs) have the breadth of testing services required for full biopharmaceutical analysis. Not surprisingly, an estimated 70%-80% of ADC analysis is outsourced.[6]

ADC analysis also requires expertise handling highly cytotoxic compounds. Because the potency of ADC payloads is much greater than biologic drugs, it is crucial to truly understand the role that each part of the ADC – mAb, linker and cytotoxic agent – plays in the toxicity, stability and safety of a new drug.[7]

Linkers: improvements in linker design focus on serum stability and drug-to-antibody ratio (DAR). The overall concern with linkers is to produce more homogenous ADC populations by studying the conjugation between linker and mAb.

Payloads: choosing the right payload involves certain basic criteria, such as solubility, stability, and the likelihood of conjugation.[11] But ascertaining the correct drug potency also has proven to be a critical factor. According to McCombs et al, “poor clinical efficacy of first-generation ADCs is attributed to sub-therapeutic levels of drug reaching the target.”[10]

The IND analytical package must include not only assays and purity analyses, but also the drug-to-antibody ratio (DAR) and site(s) of conjugation. Only advanced biopharmaceutical analysis can supply this information.

Selecting the right analytical techniques is critical.[13] Valliere- Douglass et al. suggest that conventional analytical methods used for standard biopharma characterization are not sufficient for ADCs.[14] They outline the latest methods in mass spectrometry that have helped scientists fully characterize ADC drugs when conventional techniques fall short.

A list of analytical services and techniques necessary for ADC characterization is given in Part 4 of this white paper.


2.2 Challenge #2 – Failure to provide sufficient CMC data 
One of the primary reasons IND submissions for new ADCs are delayed is because the biopharma company (or their contract service provider) fails to perform analyses in accordance with Chemistry, Manufacturing and Controls (CMC) guidelines.[15]

This is because nine times out of ten, the drug developer lacks a clear plan for meeting CMC data requirements when mapping the development process.16 In fact, a key factor in streamlining your IND submission for a new ADC is finding a development partner who can help you articulate a well-planned CMC strategy early in the project.

Complete structural characterization, physico-chemical testing, and biophysical analysis of the antibody-drug conjugate are required. This includes the parent monoclonal antibody, as well as analysis of biological activity, toxicity, and stability of the drug product. Table 1 on the following page shows the structural analysis needed for the mAb intermediate.

As already mentioned, ADC analysis is more complex than traditional biopharmaceutical analysis. Multiple biopharma studies and analytical methods are required, as well as concurrent expertise in performing these techniques and interpreting the data.

Analysis Needed Appropriate Analytical Technique
Primary Structure (Complete Sequence) Peptide map-UPLC-UHR QToF
Disulfide linkage Peptide map-UPLC/MS/MS
Secondary/tertiary structure CD, Fluorescence, HDX-MS
Fragments Aggregates SEC-MALS, MFI
Charge icIEF
Glycosylation Peptide map-UPLC/MS/MS or cleavage/labeling/UPLC
Ohter post translational modifications Peptide map-UPLC-UHR-QToF
Antigen binding ELISA, ECL, SPR
Biological activity, as appropriate Cell bioassay (proliferation, cytotoxicity, affector)
Table : Necessary analysis of mAb to meet CMC guidelines, and corresponding analytical techniques

Bottom line: you may find traditional techniques used for biopharmaceutical analyses are quickly becoming obsolete. New, highly sensitive and specific technologies are becoming the standard, and are indispensable if you are to progress through the clinic ahead of your competition.[17]


3.0 Why traditional approaches fall short
The complexity of the ADC molecule and lack of emphasis on CMC development strategy are the primary causes for delays in ADC IND approvals. But since most early stage developers lack internal analytical resources, they must partner with consultants or CROs who understand regulatory guidance and can help them navigate the IND process. They also need access to a full suite of cGLP and cGMP-compliant analytical testing services. But it can be difficult to find a partner with the experience and capabilities necessary to step into this role.

There are two primary reasons why the choice of outsourcing partners can be especially critical for ADC developers:[17]

Analytical Capabilities
Older techniques are unable to provide the analyses necessary for ADC molecules – the stability of specific molecules cannot be determined, and a deep understanding of the molecule may not be possible.

Absence of a Plan
All too often, early stage developers lack a defined CMC strategy. When this is the case, archived samples often aren’t set aside, validation reports and studies are inconclusive, and compatibility studies are overlooked—all of which can lead to delays and/or insufficient data. In the absence of a clearly defined testing strategy, analytical methods are not in place to ensure the identity, strength, quality, purity and potency of the drug. These are required for every New Drug Application (NDA).[18]

Finally, according to an article by Amer Alghabban in Pharmaceutical Outsourcing: “The way a pharmaceutical company contracts CROs/ CMOs has a critical and direct impact on a company’s realization of its goal”[19]

Alghabban states that many manufacturers – 45.6% in one survey–have reported quality problems with their vendors, inexperience with regulatory requirements, and 49.1% of vendors were not able to keep their promises.[19][20]

Ultimately, current practices fail to overcome the two challenges outlined in section 2 because ADC developers partner with the wrong CRO.


4.0 Three ways to streamline the IND Process for ADCs
There are proven ways to increase your chances of successfully filing an IND for a new ADC, and at the same time reduce the amount of effort and expense involved.

Complete characterization and protein analysis play the most important part in this process.[13] This means characterizing attributes such as the drug-to-antibody ratio (DAR) and sites of conjugation. DAR is a critical factor for ADCs, because it represents the average number of drugs conjugated to the mAb. The DAR value influences the drug’s effectiveness, as low toxin loading lowers potency, and high toxin loading can negatively affect pharmacokinetics (PK) and toxicity. Sites of conjugation are important, because improving site-specific drug attachment can result in more homogeneous conjugates and allow control of the site of drug attachment.[21]

There are several considerations that can accelerate time-toclinical trials for an ADC. These include:

  • Analyzing critical quality attributes, or CQA
  • Developing a defined testing plan to ensure no necessary studies are overlooked, such as compatibility and residual solvent analysis—and a schedule that ensures the most efficient and timely completion
  • Adopting platform approaches to ADC development
  • The following sub-sections will address each of these in turn.

4.1 Conduct Detailed Studies of Critical Quality
Attributes
Critical quality attributes (CQA) are biological, chemical and physical attributes that are measured to ensure the final drug product maintains its quality, safety, and potency. The precursor to defining CQAs is complete characterization of the drug product and intermediates.

Currently, characterization of the mAb intermediate is already well defined, and includes studies such as:

  • Mass Analysis — Intact, reduced, deglycosylated
  • Peptide Map (UPLC–UHR QTof MS): sequencing, Post Translational Modifications (PTMs) and disulfide linkages
  • N-Glycan Profile Site, extent and structure of glycosylation
  • Circular dichroism
  • Differential scanning calorimetry

CQAs (relating to safety and efficacy of the drug) for an ADC product also include the following additional assays:

Analysis Needed Appropriate  analytical techniques
Drug-to-antibody ratio (DAR) HIC
Drug load distribution Peptide map-UPLC-UHR QToF
Linkage sites Peptide map-UPLC-UHR QToF
Linker payload structure FTIR, UPLC/MS/MS, NMR
Table 2: CQAs for an ADC relating to safety and efficacy, and corresponding analytical techniques

Additional attributes considered CQA, due to their impact on health and efficacy include:

  • Free drug concentration
  • Antigen binding
  • Cytotoxic assays
  • Free Drug Concentration

As mentioned earlier, the FDA is concerned primarily with human safety in regards to an IND submission. With ADCs, this means they are concerned with the concentration of free drug (toxin) in the final product — both on release and on stability. While the main advantage of ADCs is their targeted specificity, any free toxin introduced into the bloodstream is a serious threat to human health and safety. Therefore, any assay used to measure free drug concentration must be exceptionally sensitive (≤1 ng/ mL). This is typically performed by UPLC/MRM/MS.

Antigen Binding
Antigen binding is vital to the efficacy and specificity of an ADC. Non-specific binding results in the death of healthy cells and toxicity. Techniques to measure binding include:

  • Enzyme-linked immunosorbent assay (ELISA) – a biochemical technique for detecting and quantifying peptides, proteins and antibodies. Multiple formats can be utilized, but all incorporate binding of an antibody to the analyte resulting in a subsequent signal (UV, fluorescence, phosphorescence).
  • Electro-chemiluminescence (ECL) – a detection method based on luminescence from electrochemical reactions. ELISA and ECL can be used interchangeably, but ECL’s greater sensitivity allows it to be used in other studies, streamlining the IND process.
  • Surface Plasmon Resonance (SPR) – a label-free method used to monitor noncovalent molecular interactions in real time. Generally considered a poor candidate for antigen binding, due to poor inter-day precision.

Cytotoxic Assays
While all of the physico-chemical analyses (CE, icIEF, SEC, etc.) provide an idea of the purity and stability of a single aspect of an ADC, they do not provide a measure of the functional stability of the entire molecule. Cell bioassays are the ultimate measure of an ADC’s activity, stability and 3-dimensional structure, as they measure the effect of all degradation pathways. Bioassays, by their very nature, are variable and are technique-dependent, making them difficult to utilize as part of your IND submission. While research quality bioassays are sufficient for drug development; a qualified, accurate cell bioassay is an absolute requirement for an IND application. Optimizing these assays to make them precise and robust requires expert and experienced scientists. They provide a method that can be confidently used for stability and post-IND formulation development. Upon IND approval, these studies should be initiated immediately, shortening formulation/ process optimization.


4.2 Perform Studies that are often overlooked
A successful IND depends on multiple studies – particularly relating to toxicology – that are often overlooked, or even neglected. This is due to a lack of planning early on in the process. And these oversights can result in delays of several months.

A number of overlooked studies should be performed prior to initiation of toxicology and other early clinical tests. These include:

  • Dose formulation
  • Infusion set/syringe compatibility
  • In-use stability
  • Residual cytotoxins
  • Dose Formulation

Toxicology studies are performed at low doses and require greater sensitivity than release/stability assays. As required by the FDA, dose formulations must be assayed for toxicology studies, to ensure the correct dose is being delivered. The typical approach is ECL or ELISA. If ECL is developed for release, it is easily adapted to these studies, streamlining the overall IND process.

Infusion Set/Syringe Compatibility
Concern has been raised about the occurrence of critical incidents related to infusion sets. Every drug developer and CRO needs to establish a set of procedures to evaluate infusion sets from their vendors, particularly in terms of drug loss to surfaces. This includes filters, pre- and post-IV bags, and tubing. Multiple concentrations and durations should be tested.

In-use Stability
According to the FDA: “The purpose of in-use stability testing is to establish a period of time during which a multiple-dose drug product may be used while retaining acceptable quality specifications once the container is opened.” [22]

The FDA recently announced a draft GIF #242 entitled “In- Use Stability Studies and Associated Labeling Statements for Multiple-Dose Injectable Animal Drug Products”. The draft will outline how to design and carry out in-use stability studies to support the in-use statements, for multiple-dose injectable drug products.22 While this focuses on animal and multi-dose studies, the draft also reflects the importance the FDA places on in-use stability for human trials, and yet they are often neglected during the IND process.

Multiple stability-indicating assays are required, including:

  • DAR
  • ECL
  • Size Exclusion Chromatography (SEC)
  • Micro Flow Imaging (MFI)
  • Residual Cytotoxins

The linkage of the payload to the monoclonal antibody is an organic chemical event involving many of the typical solvents and catalysts. Therefore, similar to traditional pharmaceuticals, both residual solvents and heavy metals must be monitored on release of the drug substance. Typical assays include:

  • DMA (Dimethylacetone)
  • DMF (Dimethylforamide)
  • THF (Tetrahydrofuran)
  • Palladium
  • Platinum

4.3 Adopt a “Platform’ Approach
The basic idea behind a platform approach is to leverage “prior knowledge” to reduce the effort needed to start clinical trials. It begins with identifying a class of molecules that show comparable characteristics, such as physico-chemical properties and stability profiles.[23]

New candidates with characteristics that match known molecules can be treated as a “next-in-class” candidates. Once comparable characteristics are validated, developers can focus additional testing on areas of difference between the new candidate and historical likenesses—reducing testing requirements and at the same time further adding to the body of shared knowledge related to the platform, and increasing the platform’s robustness. Adopting a platform approach can significantly streamline IND testing requirements, accelerating time to clinic and reducing costs. According to Bradl et al., the platform approach enabled biopharmaceutical development for toxicological studies within 14 months after receiving DNA sequences. [24] After another six months, material from GMP facilities was provided for clinical studies. This resulted in a time requirement of 20 months from DNA to Investigational Medicinal Product Dossier.[24]

Of course, a key element is actually identifying those molecules that match the definition of a “next-in-class” candidate. Careful planning in regards to methods, data, and documentation will provide a universal approach applicable to other antibody drug conjugates.

Standardization of instrumental parameters, data collection and data manipulation can speed up characterization. The necessary studies include:

1. QToF – An ultra-high resolution Quadrupole Time of Flight MS, coupled to a UPLC can provide the vast majority of characterization data. Powerful QToF software, designed specifically for proteins, deconvolutes complicated mass spectra, simplifying data interpretation. The QToF can determine:

  • Complete sequence
  • Post translational modifications
  • Glycan profiles
  • Payload linkage sites
  • Disulfide linkages

2. Release and Stability:
The majority of assays are similar for all ADCs: SDS CE, icIEF, SEC, UV, and DAR. Generic assays can be qualified directly and only modified/optimized if qualification criteria are not met.

Design method qualifications appropriate to Phase I and template protocols
Binding assays should all utilize ECL. The sensitivity of this technique allows it to be used for toxicology and compatibility studies, as well as release and stability.

Other investigations typically include prophylactic studies in anticipation of agency questions. While they are not necessarily required for the IND filing, having data to support responses to agency questions will prevent delays. By preparing data in an IND-ready format, you’ll ensure “drag and drop” of the data, greatly facilitating the process in the typical last minute rush to complete the IND.


5.0 Buyer’s Guide: Choosing the right CRO for Fast IND Submission and Approval
According to a report by Global Industry Analysts, Inc., the global biopharma market is estimated to reach U.S. $ 306 billion by the year 2020.25

With this continued market expansion, including antibody drug conjugate development, there is a greater need for contract lab support. Not only this, but there is a critical need for high-quality contract laboratory partners who understand the regulatory guidelines, can perform required risk assessments, and can develop, validate and execute challenging analytical procedures.

If you’re looking for help from a CRO to reduce risk, and increase your chances of a successful IND submission, here’s what you need to look for:

True loyalty and partnership
You need a CRO that will take complete ownership of your product, and not just treat it like another sample. A CRO that partners with you closely – and isn’t simply a vendor – means they form a core part of your team, and have a personal stake in your success. They’re hands-on, and keep you updated every step of the way. Whatever CRO you choose, be sure they make their experts available to you at all times. They should take part in meetings, telecons, kickoff calls, and be involved in every stage of the process.

Scientific expertise
Significant scientific expertise in biopharmaceutical development and biopharma services is a must. A large proportion of the CRO staff should be made up of Ph.D. scientists and biopharma veterans. The CRO should assign scientific advisors that act as connections between your team and theirs. Their expertise and scientific background means they can accurately map out the entire process, from development to IND submission.

The right experience
Ideally, your CRO should have experience supporting successful IND submissions under tight deadlines. They should also have a solid track record of working on multiple biopharma products over several years. These drugs should span a wide range, from monoclonal antibodies and antibody-drug conjugates, to biosimilars and pegylated proteins. All projects need to be backed by an exceptional regulatory record.

Flexibility
Flexibility is important when the unexpected happens. Your CRO needs to work closely with you to determine the best analytical approaches. Their flexibility (and scientific expertise) means the CRO can think outside the box when things don’t go according to plan. They can quickly identify alternative ways of getting things done. In fact, finding novel ways to characterize and understand biopharmaceutical behavior is often necessary to file a successful IND.

Full range of analytical biopharma services. The complexity and heterogeneity of ADCs mean they are exceptionally challenging to characterize. A full suite of analytical services is necessary to do this. Be sure to ask your CRO about their capabilities, and what biopharma services they offer. As mentioned in this white paper, you need to be sure your CRO won’t overlook anything, and can help you meet CMC regulations. Their scientists should be experts in these techniques and interpretation of their data. At a minimum, these techniques should include cell-based bioassay development and analysis by ultra high resolution QToF, as well as routine release and stability testing.


6.0 Case Study: CMC Suport for ADC Development
Situation
Virtual client had very aggressive timelines for submitting INDs for two antibody drug conjugates within 12 months. The Client requested complete chemistry support for the CMC section of the IND
Solution

In collaboration with the client’s scientists, EAG proposed a fast-tracked method development and validation program to meet their timelines. EAG scientists performed complete characterization of the mAb and drug product, including complete sequencing, PTMs, and glycan analysis. Developed and validated multiple methods for release and stability including: icIEF, ELISA, cell bioassay, DAR, free drug, N-linked Glycan, SEC, CE-SDS, and HCP

Outcome
All data was delivered to the client within the deadline, and both INDs were submitted on schedule
Both INDs were successful, and the FDA had no observations/ remarks regarding the EAG’s portion of the IND. Our client’s priorities changed during the study, requiring additional studies beyond the scope of the original project. We were able to accommodate these changes and still meet their deadlines. EAG scientists were fully involved in project kick-offs.


7.0 Conclusion…
Finding a CRO who can partner with you to accelerate your antibody drug conjugate IND submission is challenging. It’s not easy to determine which CROs can truly partner with you to help you achieve your objectives.

This white paper has outlined two critical challenges with ADC development. Specifically, these challenges relate to successfully filing an IND. They are:

  • The complexity of the ADC molecule
  • Failing to meet CMC regulations
  • Given these challenges, there are 3 ways to streamline the IND process:
    • Characterize all critical quality attributes
    • Perform studies that are often overlooked
    • Adopt a platform approach

Abbreviations:
ADC, antibody drug conjugate; DAR, drug-to-antibody ratio; CMC, Chemistry Manufacturing and Controls; IND, Investigational New Drug; ELISA, Enzyme-linked immunosorbent assay; ECL, Electro-chemiluminescence; SPR, Surface Plasmon Resonance.

Keywords:
ADCs, Antibody-drug Conjugates, Characterization, Chemistry Manufacturing and Controls (CMC)


August 1, 2017 | Corresponding Author:
* Glenn Petrie, Ph.D. gpetrie@eag.com

How to cite:
Petrie G, Antibody Drug Conjugate Development: Keys to Rapid IND Submission and Approval (2017), DOI: 10.14229/jadc.2017.08.04.002.


Original manuscript received: April 12, 2017 | Manuscript accepted for Publication: July 3,  2017 | Published online September 4, 2017 | DOI: 10.14229/jadc.2016.09.04.001.

Last Editorial Review: August 17, 2017

Featured Image: Capped vials on an analysis autosampler – selective focus. Courtesy: © Fotolia. Used with permission.

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Andrew Huang: “ADC’s Are Among the most Powerful Options to Increase Drugability of a mAb”

With a population of 1.4 billion [*] and a rapidly expanding economy, China has become a manufacturing powerhouse. In addition, China is pursuing a goal of becoming a major hub for international bio-pharmaceutical product research, development and manufacturing. In realizing the first steps in this ambitious goal, China has, over the past decade, become a major destination for the global pharmaceutical industry to conduct R&D activities. This growth has drastically changed the pharmaceutical landscape, challenging Chinese companies in raising the quality of their products, while, at the same time, challenging them in expanding their development and manufacturing capacity to serve both global and national markets. [1]

Partly the results of China’s population growth and increasing domestic medical needs, the country has, according to a recent report published by UBM’s CPhI China, become the world’s biggest producer and exporter of active pharmaceutical ingredients or APIs.  Today, the country is responsible for nearly 40% of global API production. But the Chinese pharmaceutical market has still huge opportunities for growth. 

With government’s increasing investment in healthcare and R&D, China offers unique opportunities for innovative products and technologies, and collaboration between global and domestic pharmaceutical companies.

According to the China Food and Drug Administration (CFDA), the government’s significant investment in healthcare led to an increased – and more innovative – R&D pipeline and a growing importance of China as center of bio-pharmaceutical development and manufacturing.  The government’s investment has also cultivated companies with capabilities that are comparable – and competitive – with North American and European R&D, putting high-cost, global-centric R&D models at a real disadvantage.

Eliminating Concern
The growth of China’s bio-pharmaceutical industry is also the result of effectively securing Intellectual Property (IP) rights.  IP rights are among the most valuable resources for pharmaceutical and biotech companies, and their  protection often dictates the future success of the companies involved. While poor IP protection and enforcement have often been cited as limiting factors in the growth of pharmaceutical companies’ drive to carry out R&D in China, recently revised patent laws have increased overall global trust and are expected to effectively deter copycat drug makers.  And while, according to the US-China Business Council, some concern remains, China’s IP laws and regulations increasingly reflect international standards, allowing Chinese authorities to better protect and enforce IP rights.[2]

According to a study about the business of life sciences, pharmaceuticals and healthcare sector in China, published by Deloitte China Life Sciences and Health Care in Shanghai, the increased IP protection and enforcement has resulted in a growing number of global pharmaceutical companies being increasingly attracted to the idea of having a R&D center in China or, alternatively, partnering with Chinese partners.[3]

Furthermore, a general low cost base, a large pool of highly qualified research subjects, increasing scientific capabilities, the local industry’s knowledge, a general lack of regulatory and cultural impediments often found in other countries and insight into the country’s growing drug markets have made China an attractive country for R&D.

Ambitious Plans
In China, regulatory approval for pharmaceutical agents is based on clinical trials that have been carried out in the country. This requirement has also contributed to the global pharmaceutical industry’s interest in conducting clinical trials in China – and, as a result, work with a Chinese contract research organization (CRO) and contract (development) and manufacturing organizations (C(D)MO).

The regulatory environment has, no doubt, boosted China’s ambitions plans to be a primary market for CROs and CDMOs. Most of the top 20 multinational pharmaceutical companies have been expanding their footprint in China by setting up R&D facilities through various enterprise structures. Large companies including Bristol-Myers Squibb (BMS), Pfizer, Roche, GlaxoSmithKline (GSK), Johnson & Johnson and Novo Nordisk continue to develop partnerships with Chinese companies.

This approach mitigates traditional development risks but also leverageg local efficiencies, allowing companies to add operational value due to familiarity with the market and regulatory requirements, leading to shortened approval times and reduced development costs. In turn, Chinese CROs are recruiting expert Chinese nationals with research experienced nurtured at top Western pharmaceuticals companies to staff domestic CROs.

Moreover, global pharmaceutical companies are starting to conduct R&D activity specifically related to Asian markets. The specificity is linked to the environmental, cultural and genetic factors, liver disease, certain cancers, and some communicable diseases that are more common in Asian countries, such as China and Thailand than in other countries around the world.

Expanding facilities
Among the growing CRO/CDMOs in China is MabPlex International. Based in Yantai, a port city in Shandong province, China, and founded in 2013, the company specializes in the development and GMP manufacturing of recombinant proteins, antibody therapeutics and antibody-drug conjugates for its global customers. To accommodate growing demand, MabPlex, in October 2016,  broke ground on the expansion of its bio-manufacturing facilities.

The construction of company’s new 428,000 sq. ft. facility is expected to be completed by August of 2017, with utility and HVAC validation finished by December 2017.  The fill/finish facility will be completely validated by March of 2018.

Earlier this year we interviewed Andrew C. Huang, MabPlex’ Senior Vice President of R&D. Huang has developed a robust and proprietary technology platform for the manufacturing antibody-drug conjugates based on covalent thiol conjugation Technology. The resulting Hertuzumab Vedotin, the first ADC being developed in China, has entered Phase I and Phase II clinical trials.

Prior to joining MabPlex International, Huang served for more than 17 years as a biomedical researcher at the University of California, Los Angeles (UCLA), a public research university in the Westwood district of Los Angeles, engaging in molecular medicine, including brain aging, diabetes, stem cells and protein folding research. He has published near 100 research articles, journal reviews and book chapters. During our interview we asked him about his company, the role his company plays in global bio-pharmaceutical development and manufacturing, the current expansion, the potential for antibody-drug conjugates and the regulatory env

Question/Peter Hofland: What excites you the most about the potential of ADCs?

Answer/Andrew Huang: Antibody drug conjugates are one form of combinatorial therapy that uses tumor-targeting antibodies and high-potency chemical drugs. Most antibodies alone have limited efficacy against malignant cancers. The efficacy of an antibody often increases synergistically when conjugated to a high-potency chemical drug. In addition to the enhancement efficacy, the ADC platform can rescue some  cytotoxic drugs, which are too toxic or have poor bioavailability on their own.

PH: What are your company’s major accomplishments over the past 12 months?

AH: We have completed several ADC projects, including providing ADCs for phase II clinical trials and one successful IND with better than expected results.

PH: … and what are your expectations for the next 12 months?

AH: Our ADC projects from US-based clients gradually increased over the last 12 months. And we expect that this will continue in the foreseeable future. That’s why we are expanding our ADC manufacturing capacity to accommodate [the doubling of the number of ADC projects].

PH: As a CDMO, what are the top three things that sets your company’s next-generation ADC platform apart?

AH: I think that there are three things that set us apart. The first thing includes our cysteine conjugate platform and our product quality in terms of conjugation efficiency and fraction of DAR4. The second differentiator is our proprietary thiol covalent conjugation technology and finally, our faster speed and efficiency of completing client’s task as compared to (other) leaders in the field.

Pharma/Industry Questions
PH: MabPlex International is based in China. How big is the role of Chinese CDMOs in the world?

AH: The Chinese are gradually increasing their role as a worldwide CDMO family. However, right now, Chinese CDMO companies are limited in capacity because most Chinese companies focus mainly on Chinese business and they are not familiar with rules and business outside China. But that’s changing. Currently, more and more Chinese companies are starting (representative) offices in the United States and Europe to explore opportunities.

PH: How is the approach of Chinese companies different (or similar) to the approach of CDMOs in North America and Europe?

AH: Most CDMO companies in China are led by US/Europe “returnees” so most approaches are likely to be the same or (very) similar. The significant difference will be to fit Chinese “culture” and how to bridge the Eastern culture to Western one.

Regulatory landscape
PH: The unique properties of ADCs create technical challenges that require careful CMC considerations. Based on your experience in the development of ADCs what are some of the current regulatory challenges (with special focus on CMC)?

AH: A few years ago, during the Cambridge Healthtech Institute’s inaugural CMC Strategies for Antibody-Drug Conjugates meeting in Boston, Massachusetts, someone answered the same question by saying that antibody-drug conjugates are conceptually, very simple, but in practice, extremely complicated.  And I must agree with that. In it’s ‘simple’ complexity ADCs combine a monoclonal antibody, a chemical linker and a cytotoxic drug. Simply stated, as a result of the complex nature of an ADC, we need triple the amount of control and characterization to achieve the right formulation, stability and consistency for effective scale up and manufacturing if we want to meet the regulatory requirements.

And with the increased number of ADCs coming down the pipeline, it becomes imperative for pharmaceutical and biotechnology companies to consider the manufacturability of the ADCs. This means that they have to incorporate process design and CMC strategies early on in the development stage of an ADC.

Looking at our experience, some of the technical challenges require careful CMC considerations include homogeneous drug distribution, the highest possible fraction of DAR4 and the lowest possible fraction of DAR6 or higher with cysteine conjugation.

PH: Overall…What do you see is the biggest challenge in the development of ADCs?

AH: That’s the degree of homogeneous drug distribution.

But manufacturing ADCs not only involves technical challenges but also challenges in the areas of externalization of manufacturing, supply chain management and new technology considerations. That’s why regulators, looking at the highly toxic nature of ADC payloads, as well as the monoclonal antibody and linker chemistry thta make up an ADC, are concerned about the safety, potency and stability of the product and the workers involved in manufacturing it.

Regulatory implications
PH: How is the regulatory landscape in China different than the European of North American regulatory landscape?

AH: A few years ago, regulations in China for CDMOs were significantly different when compared to Western regulations. At that time the drug license and MFG (Drug Manufacturing) license had to be the same. This greatly limited Chinese CDMO development. However, after November 2015, China adopted a new policy for Marketing Authorization Holders (MAH). This new policy is similar to policies in the United States and Europe: the licenses for marketing authorization and manufacturing are separate.

PH: How has the creation of the China Food and Drug Administration (CFDA) and a restructuring of its regulatory system benefited Chinese CDMOs and in particular, your company?

AH: As mentioned, starting in November 2015, China enforced a new policy for Marketing Authorization Holders similar to policies in the United States and Europe. Prior to 2015, all bio-pharmaceutical companies were required by the China Food and Drug Administration (SFDA) to complete the biologic drug CMC and formulation-fill-finish by themselves. Only a chemical drug could be outsourced or contracted out to CRO/CDMOs. Now, biologics, like any chemical drugs, can be outsourced to CRO-CDMO, like MabPlex.  This includes  R&D and CMC, formulation, fill-finish and even IND submissions.

PH: One often heard concern from companies in North America and Europe is that despite vast improvements, concerns still persist about enforcement of intellectual property (IP) and patent laws in China. How does that impact CDMO business in China?

AH: These concerns have a deep impact on CDMO’s in China. We believe the only thing we can do is to continuously improve our IP enforcement, which is already at Western standards. In addition to our secure enforcement of IP protection, MabPlex has a morning meeting each day to emphasize to all our employees three things: IP, GMP and Safety!

PH: … and how does this, specifically, impact your business?

AH: Companies, especially North American and European companies, are still a little hesitant in dealing with new companies like us. However, we see more and more companies from the United States starting ADC business with us. We are confident that we will prove to our US and European colleagues that we are a trustful and reliable partner.

PH: Your company is experienced in ADC development and manufacturing. Are you planning to expand with additional development and manufacturing facilities in North America and Europe?

AH: We already established a branch (MabPlex Inc. USA) in USA last year. But our US branch will not include manufacturing.


[*] 2017

Last Editorial Review: May 24, 2017

Photo 1.0: Andrew C. Huang, MabPlex International’s Senior Vice President of R&D. Courtesy: © 2017 MabPlex  Featured Image: MabPlex headquarters, Yantai, Shandong, China. Courtesy: © 2017 MabPlex. Used with permission.

Copyright © 2017 InPress Media Group. All rights reserved. Republication or redistribution of InPress Media Group content, including by framing or similar means, is expressly prohibited without the prior written consent of InPress Media Group. InPress Media Group shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. ADC Review / Journal of Antibody-drug Conjugates is a registered trademarks and trademarks of InPress Media Group around the world.

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Evolving CMC Analytical Techniques for Biopharmaceuticals

1.0 Abstract
During the (early) preclinical drug development process as well as manufacturing of biopharmaceutical (protein) products, analysis and characterization are crucial in gaining a better understanding of the physical and chemical properties of various materials. These properties can have an impact on the manufacturability as well as the performance, potential for metabolism, stability and appearance of a specific medicinal product. Hence, properly characterizing these products is essential for a drug candidate to move from drug development to regulatory approval and, finally, the clinic.

In recent years, complex biopharmaceutical drugs and biologics have evolved into mainstream therapeutics. The manufacturing of these compounds, including monoclonal antibodies, bispecifics, antibody-drug conjugates (ADCs), recombinant and other therapeutic proteins, require extensive analytical and comprehensive characterization using a variety of techniques, including non-compendial, and sometimes an intricate quality control methodology, to confirm manufacturing consistency and product quality.

Because biopharmaceuticals and biologics exhibit highly diverse structures and broad biological activities, a study of these agents is a relatively complex process requiring sophisticated analytical techniques. Furthermore, in addition to these complexities, regulatory expectations to better understand product impurities and degradants in biopharmaceutical products continue to increase.

As a result, many drug developers may find that their current global chemistry, manufacturing, and control (CMC) systems are quickly becoming obsolete. Consequently, new, highly sensitive and specific technologies are becoming the new normal.

Keywords: Biopharmaceutical analysis, Characterization, Protein therapeutics, Bioanalytical methods, Structure and function, Physical and Chemical properties


2.0 New Analytical Approaches
The field of monoclonal antibodies, launched with Köhler and Milstein’s initial study published in 1975 of a method to produce fully intact murine IgG antibodies, has created a new area of the development of novel medicinal products. [1] In the more than three decades since the initial development of monoclonal antibodies, chimerization, humanization and fully human antibody technology followed. [2]

Subsequent to the growth of antibody-based products, new technologies have emerged for creating modified forms of antibodies, including antibody fragments, antibody-drug conjugates or ADCs as well as bi- and multi-specific antibodies.

In the development of these next-generation medicinal compounds, a better understanding of currently approved ADCs and novel site-specific bio-conjugation technologies is required. For example, a better analytical understanding of the structure-activity relationship accelerates the discovery and development of the next-generation ADCs with defined and homogeneous compositions.

Analytical methods and characterization for novel biopharmaceuticals and biologics involve complex, multi-faceted procedures stretching from early (pre-) clinical drug discovery to clinical development, regulatory approval and, finally, market entry.

Most of this work takes place during the early development phase, and is vital to help understand the influence of process changes, measured against an established reference standard.

3.0 Protein Therapeutics
Biopharmaceutical therapeutics are inherently challenging to characterize because of their complexity and natural heterogeneity. Therefore, appropriate and complete analysis ensures meaningful and reliable characterization, and provides the data required to satisfy regulatory requirements concerning product identity, (im)purity, concentration, potency, stability, safety and overall quality.

Methods used to characterize primary and higher-order structures (including techniques to determine protein sequence, posttranslational modifications, folding and aggregation) and protein concentration (including amino acid analysis, intrinsic protein absorbance and colorimetric methods) are vital to avoid aberrant results for key attributes that could, potentially, raise quality issues.

In addition, characterization and analysis of biopharmaceutical proteins also involves product- and process-related determination of impurities, which may compromise the safety of the protein therapeutics. This includes various assays (including bioassays and noncell-based binding assays) for determining the functional activity of proteins, which may be indicative of potency.

Overall, a complete approach to characterization helps developers to be confident that their product meets regulatory requirements as well as product quality and safety standards.

4.0 Changing Technologies
While spectrophotometric analyses of proteins are commonly used, there may be a number of important reasons to change analytical methods and characterization techniques.[a]

The reasons may include:

  1. New techniques may allow for better characterization, making it possible to follow the stability of specific molecules and proteins, as well as contribute to deeper understanding of them. New techniques may include imaging, capillary-electrophoresis, ultra-high-resolution mass spectrometry, micro-flow imaging (MFI), etc.; (Figure 1.0)
  2. Improved technologies to replace legacy methods. Examples include using ultra-high-performance liquid chromatography (UHPLC), a relatively new technique giving new possibilities in liquid chromatography, instead of high-performance liquid chromatography (HPLC) and Capillary Western (WES), a quantitative western blot produced by a protein simple, which offers increased precision and specificity versus ELISA; (Table 1.0)
  3. Formulation and process changes may occur in the early stages of drug development. Even through Clinical Trial phase I and phase II, there may be formulation or process changes, which may require additional or new analytical methods;
  4. There may an interfering compound within the formulation. One example is the use of surfactants[b], such as Polysorbate 80[c] (also known as PS80) which may interfere with the reverse-phase method. To be certain about stability, when observing new degradants, it may be required to use a new method that will resolve and quantify the new analytes;
  5. There are specific regulatory requirements that apply to approved products, including the expectation of periodic method assessment for improvement;
  6. Many techniques allow for strategic business decisions, resulting in high throughput with low costs. This largely depends on how many lots and stability studies are necessary. In turn, this may directly impact the costs associated with the regulatory approval process of products being developed.

Figure 1.0 A number of recent methods developed in the past years allowing scientists to look at antibodies much more closely include ultra-high resolution mass spectrometry (UHR-MS), multiple reaction monitoring (MRM), mass spectrometry, ultra-performance liquid chromatography (UPLC)[d] analysis of glycans (both by MS and HBLC fluorescence), microfluid imaging analysis and automated Western (WES).
5.0 Regulatory Implications
The regulatory process established by the U.S. Food and Drug Administration (FDA) requires that each New Drug Applications (NDA) and Abbreviated New Drug Application (ANDA) includes the analytical procedures necessary to ensure the identity, strength, quality, purity and potency of the drug substance and drug product. [3][4] Furthermore, each Therapeutic Biologic Application (BLA) needs to include a full description of the manufacturing process. This includes analytical procedures that demonstrate that the manufactured product meets prescribed standards of identity, quality, safety, purity and potency. [5]

The analytical procedures and methods validation for drugs and biologics, Guidance for Industry, states that, over the life cycle of a medicinal product, new information (e.g., a better understanding of product characteristics) may warrant the development and validation of a new or alternative analytical method. [6]

But analytical methods should not be considered to be “locked down” or validated once clinical trial phase I or phase II is reached. To fully understand the biopharmaceutical products involved, the FDA requires scientists to consider new or alternative analytical technologies, even after completion of the drug approval process.

The FDA also requires that drug developers and manufacturers periodically evaluate the appropriateness of an analytical method and consider new or alternative methods. To make this process simpler and more robust, and in anticipation of life cycle changes in the analytical process, an appropriate number of drug samples should be archived to allow for comparative studies. These samples must not only be put away for stability studies, but a reasonable number of samples should be archived at the proper temperature (typically at -80 degrees for a biopharmaceutical sample) to be used for crossover and comparability studies. This is critical to smoothing the pathway for change from one analytical method to another. [6]

6.0 Regulatory Reporting Requirements
Establishing a regulatory framework, the FDA sets “safety reporting requirements for human drugs and biological products” that include mandatory reporting of any change in analytical methodology, and describes—among other things—a developer’s responsibilities for reviewing information relevant to the safety of an investigational drug and their responsibilities for notifying FDA. These reporting guidelines cover minor, medium and major changes. (See: Table 2.0)


6.1 Minor Changes
Minor changes are those within the “validated change of the analytical method.” For example, when a validated chromatography method for a column temperature range of 10° to 40° change from a nominal of 30° to 35°, this would be considered to be a minor change. While this change can be submitted as part of the annual report, it is still required that the applicant reports the change to the agency. [8]

The Guideline for Industry detailing the requirements for the annual report stipulates that properly reporting post-approval manufacturing changes must be made in compliance with current Good Manufacturing Practice (cGMP). [9]

6.2 Moderate Changes
At the moderate level, the validated range is exceeded in certain parameters. Such a change may have an adverse effect on the identity, strength, quality, purity or potency of the drug product. Using chromatography as an example, this could be a change in mobile phase from acetonitrile to methanol, or a change in the actual gradient of a method. Such a change has more stringent requirements and required validation of this new method in additional comparability studies.

6.3 Major Changes
Major changes include modifications that establish a new analytical method, eliminate a current method (substituting one method for another rather than adding a new method), or delete or change the acceptance criteria for a stability protocol.

At the major level, there are substantial changes to the analytical method. For example, a major change includes switching from UV detection to mass spec (MS-) detection. Such a change must be validated with a formal, highly statistical comparability study designed to show any differences, or lack thereof.

In case of a major change, developers are also required to submit and receive FDA approval of a supplemental application to the original NDA or ANDA. In what is known as a Prior Approval Supplement (PAS), a major change needs to be reported and include a detailed description of the proposed change, which products were involved, a description of the new method, the validation protocols and data, a description of the changes to evaluate the effect of the change, a comparability report, a description of the statistical method of evaluation and a final study report. [8][9]

While a PAS is generally required for approved drugs, it also sets expectations for early-phase products. Although they are not covered under formal CFR regulations, the FDA does, in fact, expect at least a similar study to be performed when a drug is in clinical trial phase I, II or III.


7.0 Comparability Study
The comparability process is critical. The FDA requires that a manufacturer carefully assess manufacturing changes and evaluate the product resulting from these changes for comparability to the pre-existing product. In such a case, the goal is to show that a new analytical method is superior to the original method. [10]

Figure 2.0: Numerous new analytical approaches and characterization methodologies have emerged that are designed to (better) analyze biopharmaceuticals, allowing scientists to look at monoclonal antibodies much more closely. The FDA expects that applicants use novel methods in lieu of older methods. [Click here for table]
Based on the guideline for industry, determinations of product comparability may be based on chemical, physical and biological assays and, in some cases, other nonclinical data. This requires referring to archived samples from historical batches, and whether those are included in the Investigational New Drug (IND) submission, clinical or registration batches. [10]

This is a critical part of the process, because developers need to show that a new method is more sensitive or selective, and is therefore detecting and quantifying impurities or degradants that were always present, but not seen by the current (existing) method and, as a result of a change of methodology, can now be better monitored.


8.0 Comparability Design
A well-planned comparability design will assess the effect of CMC changes, allowing the FDA to determine if a specified change can be reported in a category lower than the category for the same change. Appropriate samples should be included, allowing a comparison of the ability of the new and original method to detect relevant product variants and degradation. This approach provides sufficient information for the FDA to determine whether the potential for an adverse effect on the product can be adequately evaluated. [11] [12]

To be adequate, the number of batches should be statistically relevant. The guidance to industry emphasizes the use of a trained statistician. The reason is that, while the FDA recognizes that a comparability design is less complicated than a clinical trial, it requires a statistician to design a robust program clearly showing differences between methods. [11]


9.0 Concerns
There are a number of concerns associated with the development and the implementation of new methods designed to replace a current (existing) method. The biggest question is whether the results of the analytical methods will be different.

In general, the expectation is that by changing analytical methods, there is indeed a fairly high probability of getting different results. Hence, if there is a change to an improved method, the ideal scenario is a change in sensitivity or specificity, which would therefore show an additional or higher level of impurities or degradants.

Another concern is assay bias. For the statistical analysis of data, it is important that both the new and old data are within specification. Based on the guidelines to industry, the cause of bias must be examined to see if such bias has an effect on the data. Hence, analyzing archived samples to show that impurities and degradants were always present is crucial.

For products that have already been marketed, there is a concern that new impurities may result in the requirement for new, additional, clinical work. If there are archived samples to show that the materials were always there, the clinical data will still prove that the drug is safe and efficacious, and that the newly measured impurities and degradants could not be measured with the previous method.

If such is the case, statistical analysis is still necessary to justify the bias; however, there is no need for additional clinical work. The new process is just implemented to compare and show an improved method. [11][12]


10.0 Conclusion
Preclinical drug discovery and development process, as well as manufacturing of biopharmaceutical products, involves a complicated process including rigorous (experimental) scientific study. By following regulatory guidelines, successful advancement of novel drug candidates requires early planning, setting aside archived samples, having a very tight validation report and study and, finally, having a well-planned, statistically rigorous comparability study.

If these steps are present, there is a high probability of a smooth regulatory process. Drug developers may expect to receive approval to use the new analytical method for a marketed product. And if the product is in a preapproval process, the expectation is that there is no need for additional questions from the agency. 


Footnotes
[a]UV-VIS spectroscopy (ultraviolet and visible spectroscopy) is typically used for the determination of protein concentration by either a dye-binding assay or by determining the absorption of a solution of a protein at one or more wavelengths in the near UV region (260-280 nm). Circular dichroism is another spectroscopic method used in the early-phase characterization of biopharmaceuticals (proteins).
[b]Surfactants are compounds that lower the surface or interfacial tension between two liquids.
[c]Polyoxyethylene-sorbitan-20-monooleate
[d] UHPLC and UPLC (Waters Corp.) allow for better separation of peptide mapping
[e]CBE-30 is similar to Changes Being Effected (CBE) and involves a filing with the FDA to gain approval of a moderate change (this may include a change that has a moderate potential to have an adverse effect on the identity, strength, quality, purity or potency of the drug product, as these factors may relate to the safety or effectiveness of the drug product. Based on the CBE-30, the FDA has 30 days to respond prior to implementation of any change. If a filer does not receive a reply from the FDA within 30 days, it is assumed that a change is approved.
[f]Chemistry, Manufacturing and Controls (CMC) is renamed to Pharmaceutical Quality/CMC


October 21, 2016 | Corresponding Author: Glenn Petrie | doi: 10.14229/jadc.2016.10.21.001

Received: August 19, 2016 | Published online October 21, 2016 | This article has been submitted for peer reviewed by an independent editorial review board.

Featured Image: Pharmaceutical scientific researchers analyzing liquid chromatography data; Pharmaceutical industry manufacturing laboratory Courtesy: © 2016 Fotolia. Used with Permission.

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This work is published by InPress Media Group, LLC (Evolving CMC Analytical Techniques for Biopharmaceuticals) and is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Non-commercial uses of the work are permitted without any further permission from InPress Media Group, LLC, provided the work is properly attributed. Permissions beyond the scope of this license may be available at adcreview.com/about-us/permission.


Last Editorial Review: October 24, 2016

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What the Experts Teach: PepTalk 2015

This year Cambridge Healthtech Institute’s 14th Annual PepTalk, the Protein Science Week, being held in San Diego, California January 19 – 23, 2015, welcomed more than 300 high-caliber speakers to the Town and Country Resort & Convention Center to share case studies, unpublished data, breakthroughs and solutions as well as a great number of quality posters supporting and enhancing medical and scientific research. Among the may topics discussed was the latest ongoing news about antibody-drug conjugates.

Despite the relatively simple concept, in practice antibody-drug conjugates are extremely complicated. First, the underlying antibody-drug conjugate discovery and development process is complex. This process poses significant challenges in that systematic  design uses a combination of optimal conjugation strategy (e.g. lysines, cysteines, Fc glycans, non-natural amino acids), linkers (e.g. cleavable, non-cleavable), and small-molecule toxophores (e.g. MMAE, DM1, Calicheamicin, PBD dimers). Second, in addition to the complexity of unconjugated monoclonal antibodies, antibody-drug conjugates exhibit unique properties, which are derived from the linkage of a biologically produced antibody to a small molecule drug.

Therefore, when designing antibody-drug conjugates, a number of parameters need to be considered, including appropriate antigen target and the conjugation method. This complexity also requires an increased level of control and characterization to achieve the right formulation, stability and consistency for effective scale up and manufacturing that meets the regulatory requirements. Furthermore, to fully realize the goal of improved efficiency and tolerability, each of the components that make up an antibody-drug conjugate (antibody, linker and anti-cancer drug) needs to be optimized.

With more and more antibody-drug conjugates coming down the pipeline, it becomes imperative for drug developers and pharmaceutical companies to consider the manufacturability of their ADCs.  This requires incorporating process design and CMC  (Chemistry, Manufacturing and Control)  strategies early on in the drug development stage.

In addition, engineering antibody-drug conjugates for successful development also requires a thorough developability analysis which, together with cell-line productivity and cost-of-goods analysis are key in determining manufacturing feasibility. [1]

Regulatory Perspective
In the key-note presentation Wen Jin Wu, MD, PhD, a senior investigator  working for the division of monoclonal antibodies at the Office of biotechnology Products (OPS-CDER) of the U.S. Food and Drug Administration (U.S. FDA), showed how the unique properties of antibody-drug conjugates or ADCs create a number of technical challenges that require careful CMC considerations. With the increase in Investigational New Drug submissions for antibody-drug conjugates (IND) and recent approval of ADC products such as brentuximab vedotin (Adcetris®; Seatlle Genetics) and ado-trastuzumab emtansine (Kadcyla®; Genentech/Roche) the FDA has gained much in-depth knowledge regarding ADC development programs. In his presentation Jin Wu discussed the FDA experience with ADC development and the regulatory challenges, with special focus on CMC. He also discussed a strategy for the development of the next generation of ADCs. [2]

Engineering and lead optimization
Among the exhibitors, Sebastian Schlicker, PhD (Genedata AG; Basel, Switzerland) described how an enterprise workflow platform that supports a full ADC discovery process, including antibody screening and engineering, antibody expression and purification, drug conjugation and reporting of ADC-specific analytics (e.g. DAR, drug distribution, homogeneity), can be instrumental in drug development. The workflow platform, called Genedata Biologics, focuses on antibody screening, protein engineering and lead optimization, and biologics production, enables the registration and tracking of large panels of potential antibody-drug conjugate candidates, and integrates results from analytics and functional assays in one integrated system, thereby substantially increasing throughput and efficiency of the antibody-drug discovery process. [3]

Light and ADCs
Scientists have long known and confirmed that chemical and physical stability problems may arise when antibody-drug conjugates are exposed to light.  These stability problems may be caused when the conjugated drugs act as photo-sensitizer (e.g., CBI, duocarmycin or an anthraquinone moiety), and/or the conjugation of drug moieties to antibodies changes the sensitivity towards light exposure.  In his talk Christian Schöneich, PhD, Takeru Higuchi Distinguished Professor and Chair, Departments of Pharmaceutical Chemistry, School of Pharmacy, University of Kansas, focused on light-induced photo-degradation of ADC mimics, designed to evaluate the light-sensitivity and degradation mechanisms of ADCs. [4]  Understanding degradation pathways and the mechanisms involved is important because the degradation of the ADC may interfere with the intended biological activity. In turn, this understanding has enabled pharmaceutical scientists to propose various stabilization strategies.

Crossing the Blood-Brain Barrier
Among the very interesting posters at PepTalk was one presented by Xiaocheng Chen, PhD.  Her team at Genentech has been involved in the research of receptor-mediated transcytosis or RMT as a promising route to facilitate delivery of therapeutics across the blood-brain barrier or BBB. The blood-brain barrier is a highly selective barrier preventing molecules from freely entering the brain.  While it is designed as a gatekeeper to protect the brain and central nervous system from harm by keeping foreign substances out while permitting access only to certain metabolically essential molecules, such as glucose, insulin, and growth hormone, it also limits the access of protein therapeutics entering the brain for the treatment of disease.

Receptor-mediated transcytosis may to facilitate delivery of therapeutics across the blood-brain barrier. However, there are only a very limited number of identified receptor-mediated transcytosis targets. Furthermore, key characteristics of an ideal RMT targets remain unclear. To address these issues, Chen and her team utilized multiple approaches.  They reviewed RNAseq and proteomics methods and performed a detailed screening against potential candidates. Furthermore the researchers also looked at a number of target candidates reported in the literature.  As part of their findings, the researchers reported that two novel RMT targets have been identified.  In the therapeutic dosing study, these novel targets showed significant brain uptake. [5]

In a separate presentation, Jean Lachowicz, PhD, Chief Scientific Officer at Angiochem, Inc. discussed how, using a peptide recognized by the brain capillary endothelial cell receptor  LRP1, peptide-mAb conjugates can cross the BBB in therapeutic concentrations. Using this strategy in the development of ADCs to target brain tumors has resulted in significant decrease in tumor size and prolonged survival in mice. [6][7]

Homogeneity: Necessary but not sufficient
While homogeneity of antibody-drug conjugates is necessary, it is insufficient to ensure ‘best-in-class conjugation.  In his presentation Trevor Hallam, PhD, Cief Scientific Office of Sutro Biopharma, Inc. who was instrumental in shaping his company’s biochemical synthesis technology to generate a disruptive discovery and manufacturing platform for novel bispecific and antibody-drug conjugates protein therapeutics, showed that conjugation positional analysis is fundamental. Hallam demonstrated that combining two or more mechanistically diverse warheads precisely in a single ADC is possible and that novel, next-generation antibody-drug conjugates have the potential to efficiently kill tumors while limiting their ability to develop resistance to the cytotoxic conjugates. He explained that a systematic analysis of linker ‘warhead’ positioning reveals the key differences in the in vivo killing potency of solid tumors that are not predicted by internalization rates, binding affinity, stability or PK, and may show differences in the tumor drug disposition. [8]

Other presentations
Building on the success of established ADC platforms, approved for the treatment of patients with cancer, means looking beyond currently approved agents. The vast majority of these agents utilize derivatives of maytansine and auristatin.  While these agents have proven to be successful,  John Labmert, PhD, Executive Vice President and Chief Scientific Officer at ImmunoGen, Inc., in his presentation described exciting advances in the development of payloads with different killing mechanisms.[9] Building on this knowledge, Vishal Verma, PhD, a scientist, medical chemistry, at Genentech, Inc., who’s current work focuses on incorporating medicinal chemistry aspects of drug discovery to linker and drug design for antibody-drug conjugates, discussed how the identification and evaluation of novel payloads for the next-generation of ADCs will be instrumental in addressing the current shortcomings.[10]

Adeela Kamal, PhD, Associate Director, Oncology Research at MedImmune, responsible for leading ADC efforts as wel as managing other preclinical oncology research, discussed her company’s strategies in identifying high value tumor targets,  applying state-of-the-art ADC technology with novel payloads, site-specifuc conjugation, and, finally, how to advance ADC programs in the clinic.[11]

With leaders from around the world, the organizers of PepTalk – The Protein Week, one of the largest gatherings of protein science researchers in the United States, demonstrated again, beyond doubt, their ability to present valuable, information-rich, content to more than 1,200 attendees.


Photo: Downtown, Diego, CA.  Photo Courtesy: Brianza Nyborg.

Last Editorial Review: January 26, 2015

Copyright © 2015 InPress Media Group. All rights reserved. Republication or redistribution of InPress Media Group content, including by framing or similar means, is expressly prohibited without the prior written consent of InPress Media Group. InPress Media Group shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. ADC Review / Journal of Antibody-drug Conjugates is a registered trademarks and trademarks of InPress Media Group around the world.

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