Immunogenicity: A Comprehensive Overview PDF

WHAT IS IMMUNOGENICITY? FDA Definition: Host immune response against a therapeutic protein ▪ Typically studied in the context of the formation of Anti-Drug Antibodies (ADA) ▪ All biotherapeutics include a section on immunogenicity in their FDA-approved label (Section 6.2) ▪ This is with...

WHAT IS IMMUNOGENICITY? FDA Definition: Host immune response against a therapeutic protein ▪ Typically studied in the context of the formation of Anti-Drug Antibodies (ADA) ▪ All biotherapeutics include a section on immunogenicity in their FDA-approved label (Section 6.2) ▪ This is within the Adverse Reactions section of the label  INCIDENCE OF IMMUNOGENICITY Extremely variable and dependent on numerous drug- and patient-related factors Do NOT memorize these numbers! Key Information ▪ Immunogenicity incidence is highly variable ▪ Incidence ranges from 0% to nearly 50% of subjects ▪ This makes it extremely difficult to predict and mitigate MP Baker, HM Reynolds. Self/Nonself. 1(4);314-322 (2010).  REPORTING IMMUNOGENICITY ▪ Immunogenicity data is frequently present in the label of biotherapeutics, although the amount of information included is variable ▪ Graphical presentation of the impact of immunogenicity is shown in the context of pharmacokinetics and efficacy ▪ Data is usually stratified by ADA status to allow easy identification of the impact of immunogenicity YMC Wang, J Wang, et al. AAPS J. 18(2);395-403 (2016).  EFFECTS OF IMMUNOGENICITY ON SAFETY/EFFICACY ▪ ADA impact on safety and efficacy may be displayed in many ways ▪ Generally, ADA will reduce both efficacy and safety ▪ This is through the following mechanisms: ▪ Neutralizing drug activity ▪ Accelerating drug elimination ▪ Formation of immune complexes C Passey, S Suryawanshi et al. AAPS J. 20(2);35 (2018).  TYPES OF ANTI-DRUG ANTIBODIES Know the two main classes of ADA: 1. Binding: Interacts with the drug molecule but does not inhibit its binding to the pharmacologic target a) May impact pharmacokinetics b) May impact safety 2. Neutralizing: Directly blocks interaction of drug with its pharmacologic target a) Loss of efficacy b) May impact pharmacokinetics c) May impact safety GR Gunn, DCF Sealey et al. Clin Exp Immunol. 184(2);137-146 (2016).  ‘CLEARING’ ADA ▪ Both binding and neutralizing ADA can be categorized as ‘clearing’ ▪ ‘Clearing’ ADA are detected based on their effects on pharmacokinetics ▪ Non-clearing ADA are also referred to as ‘sustaining’ ADA ▪ Typical expectations: ▪ Rapid decrease in plasma drug concentrations upon ADA development ▪ Decreased plasma concentrations following multiple dosing (typical expectation is accumulation on multiple dosing) L Liu. Protein Cell. 9;15-32 (2018).  WHAT CAUSES IMMUNOGENICITY? Short Answer: Host immune system recognizes the drug as ‘non-self’ ▪ Immunogenicity is caused by molecular, product, antigen, and patient factors ▪ Certain factors are more well-understood than others (which is what we will focus on) ▪ Key Point: Development of immunogenicity is multi-factorial in nature V Strand, J Goncalves, et al. Nat Rev Rheumatol. 17;81-97 (2021).  PHYSIOLOGIC DRIVERS OF IMMUNOGENICITY Immunogenicity is largely thought to be a T-cell dependent phenomenon ▪ The context of presentation to T-cells is likely a driver of ultimate response ▪ Presentation to Thelper cells leads to ADA generation ▪ Presentation to Treg cells limits ADA generation ▪ Amino acid sequences in proteins known as ‘T cell epitopes’ and ‘Tregitopes’ are thought to drive whether an immunogenic response occurs V Jawa, F Terry et al. Front Immunol. 11;1301 (2020).  ‘HUMAN-NESS’ DRIVES IMMUNOGENICITY Increasing the human content of the primary (amino acid) sequence decreases immunogenicity ▪ Non-human IgG sequences are more readily recognized as ‘non-self’ by the immune system ▪ All mAbs being developed now are either humanized or fully human ▪ mAbs with mouse Fc are eliminated more rapidly and need more frequent dosing ▪ Dosing frequency seems to correlate with immunogenicity as well M Sauerborn. Handbook of Therapeutic Antibodies, 2e. (2014).  ROUTE OF ADMINISTRATION IMPACTS IMMUNOGENICITY Subcutaneous and intramuscular injections are often more immunogenic than intravenous dosing. ▪ Injection into these spaces puts the drug near antigen-presenting cells, namely dendritic cells ▪ Proteins must travel through lymph nodes to reach the systemic circulation following SC/IM dosing ▪ Injections may lead to local inflammation, which further primes the immune system for response N Jarvi, SV Balu-Iyer. BioDrugs. 35(2):125-146 (2021).  ANTI-INFLAMMATORY DRUGS REDUCE IMMUNOGENICITY Low dose methotrexate reduces ADA development against adalimumab in patients ▪ Low dose methotrexate (15-17.5 mg/wk) is frequently used as an anti- inflammatory in the treatment of rheumatoid arthritis ▪ In combination with adalimumab (Humira, anti-TNF), methotrexate reduces ADA incidence in a dose-dependent manner and increases serum adalimumab concentrations ▪ This is noted in the Humira package insert ▪ Other immunosuppressive agents have been shown to reduce ADA development, including corticosteroids and B-cell depleting agents (e.g., rituximab) ▪ Long term treatment with immunosuppressives is not desirable SL Goss, CE Klein et al. Clin Ther. 40(2);309-319 (2018).  A PRIORI PREDICTION OF IMMUNOGENICITY ▪ T cell epitopes are peptide sequences that are presented by MHC and bind to the T-cell Receptor ▪ Increased content of T cell epitopes generally leads to a higher risk of immunogenicity ▪ In silico tools are available that can be used to ‘de-risk’ molecules by identifying potential immunogenicity liabilities ▪ These tools general focus on T-cell and B-cell epitopes AS De Groot, W Martin. Clin Immunol. 131(2);189-201 (2009).  QUANTITATIVE APPROACHES TO PREDICT IMMUNOGENICITY ▪ Complex mathematical models have been developed to predict immunogenicity in patients ▪ This is still an extremely new and active area of research ▪ We still cannot predict what individuals will develop ADA just the risks based on the cumulative data AM Kierzek, TP Hickling et al. CPT Pharmacometrics Syst Pharmacol. (8(11);773-776. (2019).  HEMOPHILIA A ▪ X-linked clotting disorder characterized by deficiency or absence of coagulation FVIII ▪ Affects 1:5,000 males ▪ 3 categories: ▪ Severe: < 1% normal FVIII ▪ Moderate: 1-5% normal FVIII ▪ Mild: 6-40% normal FVIII ▪ Characterized by spontaneous bleeding, mainly into large joints ▪ Standard of care: replacement therapy with plasma-derived or recombinant FVIII E Berntorp, K Fischer et al. Nat Rev Dis Primers. 7;45 (2021).  IMMUNOGENICITY TO FVIII PRODUCTS Severe hemophilia A patients have a high incidence of neutralizing antibody development ▪ Roughly 1/3 of moderate and severe hemophilia A patients developed inhibitory ADA within 50 days of initiating treatment ▪ Why? Patients with genetic defects in FVIII likely did not develop central tolerance to FVIII ▪ Impurities in plasma derived products and alternative post-translational modifications in recombinant products also contribute ▪ FVIII is therefore recognized as a foreign protein by these patients ANL Prezotti, DMdC Rocha et al. Res Pract Thromb Haemost. 5(Suppl 2) (2021).  CAN WE RESTORE TOLERANCE TO FVIII? Clinical protocols to restore tolerance are expensive and may involve immunosuppression ▪ Clinically used protocols: ▪ Bonn Protocol: High dose FVIII 2x/day ▪ Van Creveld Protocol: High dose FVIII 3x/week ▪ Malmo Protocol: Continuous FVIII for 10-14 days + cyclophosphamide + IVIG ▪ Mechanism of action is unclear ▪ Hypothesis is that ‘constant’ exposure to FVIII under non-inflammatory conditions down- regulates ADA response SJ Schep, REG Schutgens et al. Blood Rev. 32(4);326-338 (2018).  HOW SHOULD WE DEFINE IMMUNE TOLERANCE? From NIAID: “Tolerance is the prevention of an immune response of a particular antigen.” ▪ Tolerance is antigen-specific ▪ Tolerance to one protein should not induce hypo-responsiveness to an unrelated drug ▪ Tolerance should involve cellular responses and not just depletion of ADA ▪ Decreased dendritic cell maturation ▪ Increased regulatory T cells ▪ Decreased memory B cells FY Glassman, R Dingman et al. Immunol Invest. 49(7); 858-874 (2020).  MAINTENANCE OF SELF-TOLERANCE Apoptosis (programmed cell death) must result in tolerance to prevent autoimmunity ▪ Exposure of phosphatidylserine is a key step in apoptosis that promotes engulfment by phagocytes ▪ Phosphatidylserine is normally confined to the inner leaflet of cell membranes A Tajbakhsh, N Farahani et al. Int Immunopharmacol. 90;107177 (2021).  APOPTOTIC MIMICRY TO INDUCE TOLERANCE Hypothesis: Co-exposure of a therapeutic protein and PS should promote a tolerogenic response. Antigen Specificity Regulatory T Cells ▪ Co-exposure of FVIII and phosphatidylserine induces immunologic tolerance in preclinical species ▪ Antigen Specificity: Reduced ADA development only against FVIII and not an irrelevant antigen ▪ Cellular Involvement: ▪ Increased generation of regulatory T cells ▪ Decreased dendritic cell activation ▪ Reduced memory B cells P Gaitonde, R Ramakrishnan et al. J Biol Chem. 288(24);17051-17056 (2013). R Ramakrishnan, A Davidowitz et al. J Pharm Sci. 104(8);2451-2456 (2015).  CO-DELIVERY OF ANTIGEN AND DRUG FOR TOLERANCE Hypothesis: By co-delivering immunosuppressive and antigen, local effects should dominate. Co-Delivery Needed Prevention of Immune Response ▪ Rapamycin (Sirolimus): Potent immunosuppressive mTOR inhibitor (blocks T, B cell activation) ▪ Co-encapsulation of rapamycin and antigen was necessary to reduce ADA development ▪ Robust tolerance induction was observed RA Maldonado, RA LaMothe et al. Proc Natl Acad Sci USA 112(2);E156-E165 (2015).  CLINICAL TRIAL OF NP CO-DELIVERY OF ANTIGEN/RAPAMYCIN ▪ Pegloticase: PEGylated uricase used to treat gout patients that don’t respond to other treatments ▪ Pegloticase is highly immunogenic ▪ Clinical trials showed that the nanoparticle from the last slide did the following ▪ Reduced ADA development against pegloticase ▪ Allowed sustained improvement in disease severity E Sands, A Kivitz et al. Nat Commun. 13;272 (2022). HSB Baraf, PP Khanna et al. Rheumatology. Kead333 (2023). SUMMARY ▪ Immunogenicity has the potential to adversely affect pharmacokinetics, safety, and efficacy of biologics (protein drugs, cell therapy, gene therapy) ▪ The main types of ADA are ‘neutralizing’ and ‘binding’ ▪ Immunogenicity is driven by drug, formulation, patient, and disease related factors making it very challenging to predict in individual patients ▪ Mechanistic approaches to restore tolerance should be antigen specific and involve cellular components of the immune system