Dr. Kedar Purnapatre Warns That Immunogenicity’s Hidden Signals Are the Next Frontier of Biopharmaceutical Safety
The Director of Bioanalytical Operations at Aragen Biosafety Solutions delivers a technically precise and industrially grounded argument at PharmaCore India 2026: the current regulatory practice of treating anti-drug antibodies as the sole measure of immunogenicity is dangerously incomplete — and India’s growing biologics ambition demands a more sophisticated approach, Rashmi Kumariof Neo Science Hubreports from Jio Centre, Mumbai
There is a particular kind of scientific talk that operates on two levels simultaneously — the technical and the strategic — and manages to be essential to both the laboratory scientist and the boardroom executive. Dr. Kedar Purnapatre, Director of Bioanalytical Operations at Aragen Biosafety Solutions Limited (formerly Intox Private Limited, a wholly owned subsidiary of Aragen Life Sciences), delivered exactly that kind of talk at the afternoon Expert Insights session of PharmaCore India 2026 on Wednesday, in a presentation that carried the somewhat disarming title, “Unmasking Hidden Immune Responses.”
The word “hidden” in that title is doing significant scientific and regulatory work, and Dr. Purnapatre spent his thirty minutes unpacking precisely what it means — and why failing to understand it represents an increasingly costly blind spot as India’s biopharma industry graduates from small-molecule generics and conventional biosimilars toward the more complex, more immunologically active frontiers of mRNA therapeutics, cell and gene therapies, antibody-drug conjugates (ADCs), and bispecific antibodies.
The Company and the Context
Dr. Purnapatre opened with a brief but important institutional announcement: Intox Private Limited — the OECD GLP-certified preclinical safety and clinical bioanalysis organisation that has operated for over 25 years as a subsidiary of Aragen Life Sciences — has formally renamed itself Aragen Biosafety Solutions Limited, effective just days before the PharmaCore conference. The rebrand is more than cosmetic; it signals the organisation’s strategic positioning as India’s biologics CRO sector grows in complexity and global ambition. Aragen’s bioanalytical operations support biosimilars, vaccines, novel biologics, and cell and gene therapy programmes through end-to-end bioanalytical, method development, and regulatory compliance services.
The company operates through a network of sites in India and Morgan Hill, California, with a team of over 3,700 scientists and 450-plus PhDs, and has enabled over 400 customers to advance their research programmes from discovery through commercialisation. Dr. Purnapatre described the six-site footprint: Hyderabad for medicinal chemistry and high-throughput screening; Bengaluru for oncology and inflammatory models; a cGMP biologics production unit capable of 2,000-litre fermentation; the OECD GLP-accredited Pune campus — his home base — for regulatory safety and clinical bioanalysis; the Vizag campus for CGMP-grade API production; and Morgan Hill for cell line development and in vivo efficacy studies.
His broader point, made with the quiet confidence of someone who has spent two decades watching India’s CRO sector evolve, was that the service industry now represents India’s next major biopharma growth engine — not merely as support infrastructure for product companies but as a primary employer of high-value scientific talent. “The biggest employment is going to be in the service industry,” he said. “That is the next big change happening in India.”
Immunogenicity Is Not Just ADA
Dr. Purnapatre’s scientific argument opened with a foundational corrective. The pharmaceutical industry has operationally collapsed a complex biological phenomenon — immune response to therapeutic proteins — into a single measurement: the Anti-Drug Antibody (ADA) titre. The current regulatory convention, he acknowledged, reflects a historically understandable simplification. But it is a simplification that, as therapeutic modalities grow more sophisticated, is increasingly generating dangerous gaps in the safety understanding of new biological drugs.
Immune response, he reminded the audience, is a multi-pathway system. An antigen introduced into the body can trigger innate immune response through pattern recognition receptors (PRRs such as Toll-Like Receptors and PPAR), generating cytokines that activate complement-mediated pathways. It can trigger cellular immune response through T-cell interactions. It can trigger humoral immune response through plasma cells producing antibodies. These pathways operate in parallel, interact with each other, and produce consequences that range from clinically irrelevant background noise to catastrophic autoimmunity. “Immunogenicity is more than ADA,” Dr. Purnapatre stated. “It has many aspects.”
The clinical significance of any given immune response exists on a spectrum. At one end: a response so minor that it has no measurable impact on drug efficacy or patient safety. In the middle: pseudo-allergic reactions or anaphylaxis. At the severe end: tissue inflammation and autoimmunity phenotypes that can be life-threatening. The problem is that the current industry standard — monitoring ADA titres at predefined timepoints — is structurally inadequate for identifying where on this spectrum a given response lies, or for catching responses that do not conform to expected timing, magnitude, or mechanism.
Why Immune Responses Hide
The concept of “hidden” immune responses, Dr. Purnapatre was careful to clarify, does not mean responses that are inherently undetectable. It means responses that are being missed due to identifiable, correctable technical and design failures — and that is what makes them important to address. He identified five primary mechanisms by which clinically significant immune responses are routinely missed:
The first is antibody level: when ADA titres are low, current assay sensitivity may be insufficient to detect them above the background signal threshold. The second is timing: if blood sampling windows are too narrow or too infrequent, transient responses that rise and fall between collection points are simply invisible in the dataset. The third is drug interference: in patients actively receiving a biologic therapy, the drug itself is present in the collected blood sample. Free drug in the sample competes with the assay’s detection reagents, masking ADA that is actually present — a phenomenon Dr. Purnapatre identified as one of the most technically challenging problems in clinical bioanalysis. The fourth is preclinical model mismatch: the animal species used to predict human immunogenicity may not share the relevant immune architecture for a particular molecule. The fifth is late isotype switching: early immune responses are dominated by IgM antibodies, which convert to IgG over time. If the assay is designed to detect IgG and sampling is done too early, the response appears negative — until, weeks or months later, pharmacokinetic parameters begin to change and the undetected response reveals itself through its consequences rather than its direct detection.
“Immunogenicity is not a single-signal assay problem,” he said with deliberate precision. “The immune response starts subtly. The measurements are imperfect. The critical consequences appear later than the underlying biology.” This is the defining challenge: the biology precedes the measurement, and the consequences precede both.
New Therapeutics, New Immune Mechanisms
A substantial portion of Dr. Purnapatre’s talk was devoted to mapping how the proliferation of new therapeutic modalities has multiplied both the sources and the mechanistic pathways of immunogenicity — well beyond what conventional ADA assay frameworks were designed to handle.
The pharmaceutical pipeline has moved well past monoclonal antibodies. It now encompasses peptide therapeutics (including GLP-1 receptor agonists like semaglutide, where synthetic peptide impurities can themselves induce immune responses); nucleotide therapeutics including mRNA and DNA vaccines; cellular therapeutics including CAR-T cell therapies; and oncolytic virus therapeutics. Each of these modalities presents a distinct immunogenicity challenge. mRNA constructs can activate Toll-Like Receptors and trigger innate cytokine cascades. Viral vectors — as demonstrated dramatically during COVID-19 vaccination programmes — can generate antibodies against the vector itself (anti-AAV antibodies), creating a secondary immunogenicity layer independent of the therapeutic payload. CRISPR-Cas9 gene editing can trigger immune responses through DNA leakage during the ligation process. For cardiac cell therapies, antibody-mediated clearance of engineered cells has been documented, requiring patients to undergo complete immune suppression — via agents like dasimodumab — before and after the procedure.
For ADCs — the drug class that dominated the morning sessions’ strategic discussions — the immunogenicity picture is doubly complex: antibodies can be raised against both the antibody component and the conjugated drug payload, and these so-called anti-therapeutic antibodies (ATAs) represent a hidden risk that, if not identified early in development, can invalidate an entire programme. “If they are not caught early, they remain as a hidden risk,” Dr. Purnapatre said.
The Preclinical Toolbox
Dr. Purnapatre walked the audience through the contemporary preclinical immunogenicity assessment framework — a toolbox that has expanded significantly from the traditional animal-injection-and-observe paradigm. Today’s approach begins with in silico epitope prediction (computational identification of molecular sequences likely to trigger T-cell recognition), followed by in vitro ex vivo PBMC (peripheral blood mononuclear cell) assays, in which patient or donor cells are incubated with the therapeutic molecule and cytokine secretion is measured using ELISPOT or the MSD (Meso Scale Discovery) multiplex platform. Product quality characterisation — particularly aggregation profiling and impurity mapping — runs parallel to these studies, since aggregates and process impurities are among the highest-risk immunogenicity triggers. Animal studies remain part of the toolkit, and Dr. Purnapatre made a point of defending their continued relevance against regulatory and ethical pressure to eliminate them.
“Preclinical models help to rank candidates and identify relative risk. They help to flag high-risk constructs. They guide de-immunisation if a molecule has an issue. They identify T-cell-dependent risk mechanisms. And they support clinical study design.” The animal model does not guarantee human prediction — but as Dr. Purnapatre put it, “that filter is a must.”
He illustrated this with a case study from his own laboratory: an Fc-fusion protein administered to rats in a 20-day safety study showed unexpectedly high ADA titres and systemic inflammation markers. Investigation traced the problem to formulation-driven molecular aggregation — a known tendency of fusion proteins under suboptimal storage conditions. The formulation was redesigned to eliminate aggregation, the immunogenicity signal resolved, and the molecule proceeded to clinical development. “This shows that preclinical models are helpful to guide out the risks associated with biologics.”
The Clinical Cascade and the MSD Platform
In clinical samples, Dr. Purnapatre described the standard tiered ADA detection workflow: a sensitive screening assay identifies samples above the background threshold; a confirmatory assay adds drug competition to verify specificity (if the signal disappears in the presence of drug, it confirms the antibody is drug-specific); confirmed positive samples then undergo characterisation for titre, neutralising activity, isotype analysis, and epitope mapping. The endpoint of this cascade is not just a positive/negative readout but a clinically meaningful classification: is this ADA neutralising the drug’s mechanism of action? Is it triggering hypersensitivity? Is it altering pharmacokinetics?
He highlighted the MSD electrochemiluminescence platform as the current gold standard for resolving the drug-tolerance problem — the assay interference caused by residual drug in clinical samples. The immunogenic potential of therapeutic proteins is influenced by their structure and foreignness to the immune system, with ADA capable of neutralising drug effects, reducing efficacy, and causing allergic reactions — making their detection a key part of the regulatory approval process for biologics. Dr. Purnapatre cited the MSD platform’s performance in an adalimumab (the active ingredient in Humira) case study where ADA sensitivity of 0.4 nanograms per millilitre was achieved in the screening assay, neutralising antibody sensitivity of 100 nanograms per millilitre was validated, and drug tolerance was established at 20 micrograms per millilitre — meaning the assay could reliably detect ADA even in the presence of residual drug at that concentration. He indicated that Aragen Biosafety Solutions is applying the same platform to its semaglutide clinical bioanalysis work, though contractual confidentiality precludes sharing those specific data.
Regulatory Convergence and the IgM/IgE Frontier
Dr. Purnapatre closed with a forward-looking view on where regulatory expectations are heading. The FDA and EMA, while broadly aligned on a risk-based, case-by-case approach to immunogenicity evaluation, are both pushing in the same direction: away from isolated ADA titer reporting toward integrated assessment of clinical significance. What matters is not merely that antibodies are present, but whether they are meaningful — whether they alter drug exposure, whether they neutralise pharmacological activity, whether they predict adverse events.
Two emerging requirements are reshaping assay design. The first: IgM monitoring is increasingly being insisted upon by the FDA. IgM antibodies appear significantly earlier in the immune response timeline than IgG — making them valuable early warning signals of an immune response that will later become clinically significant. The practical challenge is that positive control IgM antibodies are not commercially available in the way IgG controls are; Dr. Purnapatre described Aragen’s work developing animal-derived IgM reference standards to fill this gap. The second: IgE monitoring is becoming critical for fusion proteins and complex biologics, both of which have demonstrated tendencies to trigger IgE-mediated hypersensitivity reactions — the mechanism underlying severe allergic responses including anaphylaxis.
“Hidden immune responses are often revealed through consequences, not detection alone,” he concluded. “The goal is not just to detect ADA, but to detect clinical meaning — early enough to act.”
Q&A: AI Prediction and the Sensitivity Paradox
The Q&A session raised two questions of genuine scientific substance. The first, from an audience member, asked about the potential of AI and machine learning to predict ADA from molecular sequence or structural data — in effect, to replace or reduce the need for assay-based detection. Dr. Purnapatre’s answer was measured and technically honest: predictive models are emerging, but are not yet validated for the diversity of antibody variable-domain architectures that the full biologics landscape presents. “The proof of the pudding is we have to do the assays. If titres are very high, the probability of having meaningful ADA is higher — that is the consensus at the moment. But fine mapping has to be done.”
The second question, posed by the session chair, addressed what she called the sensitivity paradox: as detection platforms advance from Luminex to MSD to OLINK to Simoa (Quanterix) — reaching attomolar (10⁻¹⁸ molar) detection limits — where does clinically relevant sensitivity end and analytical noise begin? Dr. Purnapatre’s answer was elegant in its framing: “There has to be a balance. Therapy, disease, and detection must walk in lock step.” The analytical capability must be proportionate to — and informed by — the biological significance threshold for the specific drug and disease context. Ultra-sensitivity is not inherently better; it is only better when calibrated against a meaningful clinical outcome endpoint.
A Broader Significance
What makes Dr. Purnapatre’s talk particularly important at this moment in India’s biopharma trajectory is that the hidden immune response problem is not a mature-market luxury concern. It is directly relevant to the specific products that India is being called upon to develop: biosimilars requiring extensive comparability evidence, novel biologics for rare diseases being developed for the first time in a resource-constrained environment, mRNA platforms with novel immunostimulatory mechanisms, and cell and gene therapies whose safety profiles are, by definition, incompletely characterised. Intox/Aragen’s preclinical safety and bioanalysis work has enabled clinical trials in India, Africa, Europe, Thailand, Australia, and multiple other countries — a track record that demonstrates what rigorous, globally compliant immunogenicity assessment infrastructure based in India can already achieve. The argument Dr. Purnapatre was implicitly making is that this infrastructure needs to grow, deepen, and be applied earlier — not as a regulatory compliance checkbox, but as a scientific safeguard for the patients at the end of every development programme. The Bioanalysis Group of India, which Dr. Purnapatre founded — a Sunday discussion forum modelled on the European Bioanalysis Forum that publishes posts and books on emerging topics in bioanalysis — represents his effort to build that scientific community from the ground up, one conversation at a time.
SPEAKER PROFILE
Dr. Kedar Purnapatre, PhD Director, Bioanalytical Operations, Aragen Biosafety Solutions Limited (formerly IntoxPvt. Ltd., subsidiary of Aragen Life Sciences) | Pune PhD, Molecular Biology, Indian Institute of Science (IISc), Bengaluru 50+ publications | 2 patents | 8 book chapters | Co-editor, 4 books Previous roles: Daiichi Sankyo; Ranbaxy Laboratories; University of Missouri Areas of focus: Bioanalysis, immunogenicity, ADA/NAb assay development, cell & gene therapy bioanalysis, vaccine bioanalysis Founder: Bioanalysis Group of India
KEY TECHNICAL CONCEPTS FROM THE SESSION
ADA (Anti-Drug Antibody) — immune response to a therapeutic protein; current industry standard for immunogenicity measurement, but insufficient alone | Hidden immune response — clinically significant immune signals missed due to assay insensitivity, timing errors, drug interference, or model mismatch | PBMC ex vivo assay — incubation of donor peripheral blood mononuclear cells with therapeutic molecule; cytokines measured by ELISPOT or MSD multiplex | MSD platform — electrochemiluminescence-based bioanalytical technology enabling high-sensitivity ADA detection with superior drug tolerance | IgM monitoring — early-appearing antibody isotype now required by FDA; precedes IgG and provides earlier warning of immune response | IgE monitoring — hypersensitivity-associated antibody isotype; critical for fusion proteins and complex biologics | Neutralising antibody (NAb) assay — confirms whether ADA binds to the pharmacologically active domain, reducing drug efficacy | Epitope mapping — identifies the specific molecular site on the therapeutic protein to which antibodies bind
