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Licensure of New Pneumococcal Vaccines For Adult Indications Vaccines and Related Biologic Products Advisory Committee Meeting November 17, 2005 Douglas Pratt, MD, MPH DVRPA/OVRR/CBER
Overview of CBER Presentation • Regulatory background of PNEUMOVAX 23 • Clinical endpoint efficacy/effectiveness study scenarios • Immunologic endpoints and regulatory pathways • Opsonophagocytic antibody (OPA) • Other considerations • NP colonization; accelerated approval • Summary
PNEUMOVAX 23 (Merck) • Purified polysaccharides of 23 of the most common pneumococcal serotypes (23V PS) • 1977: 14-valent vaccine licensed (50 µg/serotype) • 1983: 23-valent vaccine licensed (25 µg/serotype) • Licensed Indication: • Routine use in adults age ≥ 50 yrs • ACIP Recommendations: • Routine use in adults ≥ 65 yrs
PNEUMOVAX 23: Indication and Usage PNEUMOVAX 23 is indicated for vaccination against pneumococcal disease caused by those pneumococcal types included in the vaccine. Vaccination is recommended for selected individuals including: Immunocompetent persons: Routine vaccination for persons 50 years of age and older Persons aged ≥ 2 years with certain cardiac, pulmonary, or liver diseases, asplenia, persons living in special environments Immunocompromised persons: Persons aged ≥ 2 years with HIV, leukemia, lymphoma, Hodgkins disease, generalized malignancy, chronic renal failure, nephrotic syndrome, receiving immunosuppressive therapy, organ or bone marrow transplant.
PNEUMOVAX 23: Efficacy Basis for Licensure • South African gold miner study of 12-valent vaccine • Mean age ~22 yrs; began enrollment in 1974
PNEUMOVAX 23: Reformulation14-valent (50 µg) to 23-valent (25 µg) • Clinical immunogenicity and safety study • Adults age 21-64 years 2-fold Rise (RIA) 22-valent 50 µg N= 23 100% 22-valent 25 µg N= 29 87-100% • Type 33 added at 25 µg • Safety: minor adverse reactions in 5-25%; severe reactions unusual; favorable risk/benefit
Effectiveness of 23V PS in the Elderly and High-Risk Groups • Multiple observational studies and meta-analyses • Studies of have yielded variable results • ACIP recommendations for routine use in adults ≥ 65 years of age based on: • Case-control studies • Prevention of invasive disease, 56% to 81% • Effectiveness for non-bacteremic disease has not been demonstrated.
Effectiveness of 23V PS in the Elderly and High-Risk Groups Jackson LA et al. NEJM 2003; 348: 1747 • Retrospective cohort study, N >47,000 • Persons ≥ 65 yrs • Effectiveness of 23V PS: • Pneumococcal bacteremia: 44% (95%CI: 7%, 67%) • All cause pneumonia: No effect French N et al. Lancet 2000; 355: 2106 • HIV-infected Ugandan adults, N= 1392 • Randomized, placebo-controlled • No efficacy for any pneumococcal outcome
New Pneumococcal Vaccines: Efficacy Endpoint Considerations • Clinically Meaningful • Evidence of Benefit to the Individual • Feasibility
Clinical Trial Considerations: Age of Study Population • ≥ 65 years (high-risk) • May be difficult to study in randomized placebo-controlled trials • Ethical concerns about delaying a recommended vaccine • Many elderly already vaccinated with 23V PS • 50-64 years (moderately high-risk) • Placebo-controlled trials may be feasible • May not predict effectiveness in higher risk groups
Efficacy and Effectiveness Trials Scenarios: Age 50-64 years • Invasive pneumococcal disease • All cause community acquired pneumonia (CAP) • Presumptive pneumococcal pneumonia
Scenario 1: Efficacy Trial for Invasive Pneumococcal Disease • Invasive Pneumococcal Disease Endpoint • Sterile body fluid isolate of vaccine type pneumococcus • Age range 50-64 years • Placebo control, 1:1 randomization • Rate of invasive disease: 25-50/100,000 per year • 2.5 years of follow-up for case ascertainment • Assume 60-85% of invasive pneumococcal disease covered by serotypes in new vaccine • 90% power
Scenario 1: Efficacy Trial for Invasive Pneumococcal Disease Assumptions and Sample Size Estimates (50-64 yr)
Effectiveness Trials • Vaccine “effectiveness” trials evaluate less specific disease case definitions (e.g., all cause pneumonia) • Effectiveness estimates may be low (<50%) • Effectiveness studies are generally supported by separate culture-confirmed studies
FluMist Example: Effectiveness Trial Supporting Licensed Indication Prevention of Influenza-like Illness in Adults (18-49 yr) • Reduction of: Any febrile Illness 10.9% (-5%, 24%) Severe Febrile Illness 19.5% (3%, 33%) Febrile URI 23.7% (7%, 38%) • Provided the primary basis of effectiveness of FluMist in adults • Prevention of culture-proven influenza in children had been demonstrated
Scenario 2: Effectiveness Trial for All Cause Community Acquired Pneumonia • Pneumonia Endpoint • Hospital Discharge Diagnosis • Age range 50-64 years • Placebo control, 1:1 randomization • Rate of CAP: 300-600/100,000 per year • 2.5 years of follow-up for case ascertainment • Assume 60-85% of pneumococci covered by vaccine • 90% power
Scenario 2: Efficacy Trial for All Cause Community Acquired Pneumonia (CAP) Assumptions and Sample Size Estimates (50-64 yr)
Presumptive Pneumococcal Pneumonia: Increase Specificity of Diagnosis • Fever, productive cough • Chest X-ray • Sputum gram stain/culture (+/-quantitative) • Quantitative urine antigen • C-reactive protein/procalcitonin • Nucleic acid amplification (e.g., PCR) • Serology
Scenario 3: Presumptive Pneumococcal Pneumonia Endpoint • Presumptive Pneumococcal Pneumonia Endpoint • CXR; sputum culture, Gm stain; urine antigen • Age range 50-64 years • Placebo control; 1:1 randomization • Rate of Pneumococcal CAP: 100-200/100,000/year • 2.5 years of follow-up for case ascertainment • Assume 60-85% of pneumococci covered by vaccine • 90% power
Scenario 3: Efficacy Trial for Presumptive Pneumococcal Pneumonia Assumptions and Sample Size Estimates (50-64 yr)
Clinical Efficacy Trial Designs among Persons ≥ 65 year old • Delay 23V PS, use placebo control i.e., New Vax vs. placebo • Might be acceptable in well-monitored study • Evaluate efficacy over background of 23V PS i.e., New Vax + 23V PS vs. 23V PS • For non-bacteremic disease endpoint in this population, 23V PS may be similar to placebo control
Clinical Efficacy Trial Designs among Persons ≥ 65 year old • Compare to licensed 23V PS vaccine i.e., New Vax vs. 23V PS • Non-inferiority or superiority design • Endpoint: All pneumococcal disease • Three arm study: i.e., New Vax vs. placebo vs. 23V PS • Power for comparison to placebo
Immunologic Evaluation:Comparison to 23V PS in Adults • Inferred efficacy based on non-inferiority comparison to a licensed vaccine • Regulatory pathway has precedent e.g., Menactra™ compared to Menomune® • Approach consistent with advice of 2001 VRBPAC regarding licensure pathways for new pneumococcal conjugate vaccines for infants • For infants, comparative assessment of antibody concentration as measured by standardized ELISA
Effectiveness Based on Immunologic Critieria: Considerations • Immunologic criteria based on infant studies are not valid criteria for adults • Antibody levels that correlate with protection in older adults and elderly have not been identified • Vaccine evaluation in adults more dependent on induction of serum opsonic antibody titers
Opsonophagocytic Antibody (OPA) • A measure of functional antibody (vs. binding antibody) • Central role in protection against pneumococcus • In vivo protection mediated by antibody binding to bacterial surface, and complement-mediated uptake into phagocytic cells • In vitro assay (OPA) provides evidence of in vivo protection
Opsonophagocytic Antibody -- Unknowns • Phagocytic cells of the elderly, and other high-risk populations, may not function like the cultured phagocytic cells (HL60) used in the OPA assay • Quantitative relationship of OPA with efficacy in prospective clinical trials in adults has not yet been established • Quantitative relationship may differ by disease, i.e., invasive disease vs. pneumonia
Immunologic Evaluation:Comparison to 23V PS in Adults • Non-inferiority comparison of new conjugate vaccine to 23V PS using OPA: • For common serotypes, comparison could be straightforward • For serotypes only in 23V PS, new vaccine would fail non-inferiority comparison • How to account for missing serotypes?
Immunologic Evaluation: Superior Immune Response • Demonstration of “superior” immune response compared to licensed vaccine (23V PS) for serotypes in common: • Criteria not defined • Not demonstrated that higher antibody levels (OPA) result in greater effectiveness • Lack of precedent for regulatory decisions • Novel approach needs scientific consensus and VRBPAC agreement
Use of New Vaccine in Combination with 23V PS Vaccine: Regulatory Issues • Labeling: Indication and Usage (21CFR 201.57) • Possible implications for labeling of Pneumovax 23 • Uncertain regulatory status of new vaccine if Pneumovax 23 is not available
Pneumococcal Vaccines Targeting Non-Capsular Antigens • Immunologic comparability to infer effectiveness may not be possible • Ability to induce functional antibody (OPA) uncertain • Clinical endpoint efficacy trial in an adult population appears necessary • Efficacy endpoint studies more feasible if serotype coverage is broad
Nasopharyngeal (NP) Colonization/Carriage • Indirect effects of PCV7 thought due to prevention of NP colonization • Prevention of NP colonization • “Clinical” evidence of vaccine effect • Not direct clinical benefit for the individual • Would need acceptance as a surrogate of protection • Studies likely feasible
Accelerated Approval-- 21 CFR 601 Subpart E • Approval based on surrogate endpoint • Reasonably likely to predict clinical benefit • Applies if: • Severe, life-threatening condition • Meaningful benefit over existing treatments • Confirmatory clinical endpoint study must be completed post-licensure • Example: Fluarix (GSK)
Summary • New pneumococcal vaccines for use in adults and elderly are being developed by multiple manufacturers • Evidence of effectiveness to support licensure might be based on: • Clinical endpoint efficacy studies • Immunologic criteria (e.g., OPA) • Advice of VRBPAC sought regarding most appropriate endpoints, trial designs, and study populations to support licensure of new pneumococcal vaccines for adult indications
Marion Gruber Jingyee Kou Antonia Geber Karen Goldenthal Dale Horne Rose Tiernan Lucia Lee Margaret Bash Carl Frasch Milan Blake Acknowledgements
PNEUMOVAX 23: Efficacy Basis for Licensure • South African gold miner study of 6-valent vaccine • Mean age ~21 yrs; enrollment began in 1973