1 Date: March 10, 2008 From: Paul Kitsutani, OVRR, DVRPA Subject: Clinical Review for STN 125265/0 Rotarix: Rotavirus Vaccine, Live, Oral, GlasoSmithKline Biologicals To: Laraine Henchal, OVRR, DVRPA Through: Steve Rosenthal, OVRR, DVRPA TM 1 Rotarix BLA Clinical Review 1.1 Medical Officer's Review Identifiers and Dates 1.1.1 BLA #: STN 125265/0 1.1.2 Related IND #(s): - 1.1.3 Reviewer Name: Paul Kitsutani, MD, MPH Vaccine Clinical Trials Branch, Division of Vaccines and Related Products Applications, HFM 475 1.1.4 Submission Received by FDA: June 5, 2007 1.1.5 Review Completed: March 10, 2008 1.2 Product 1.2.1 Established Name: Rotavirus Vaccine, Live, Oral TM 1.2.2 Proposed Trade Name: Rotarix 6.0 1.2.3 Product Formulation: At least 10 median CCID50 G1[P8]; each vaccine dose contains amino acids, dextran, DMEM, sorbitol, sucrose, calcium carbonate, sterile water, and xantham 1.3 Applicant: GlaxoSmithKline Biologicals Greenford, Middlesex, United Kingdom 1.4 Pharmacologic Class or Category: Vaccine 1.5 Proposed Indication(s): Prevention of rotavirus gastroenteritis caused by G1 and non-G1 types 1.6 Proposed Populations(s): Infants 1.7 Dosage Form(s) and Route(s) of Administration: Lyophilized vaccine to be reconstituted with 1 mL liquid diluent provided in prefilled oral applicator, oral administration 2 2 Table of Contents Page 3. Executive Sumary 3 4. Significant Findings from Other Review Disciplines 4.1 Chemistry, Manufacturing and Controls (CMC) 8 4.2 Animal Pharmacology/Toxicology 9 5. Clinical and Regulatory Background 5.1 Disease or Health-Related Condition(s) Studied and Available Interventions 9 5.2 Important Information from Pharmacologically Related Products, Including Marketed Products 11 5.3 Previous Human Experience with the Product including Foreign Experience 1 5.4 Regulatory Background Information 1 6. Clinical Data Sources, Review Strategy and Data Integrity 6.1 Material Reviewed 6.1.1 BLA Volume Numbers Which Serve as a Basis for the Clinical Review 12 6.1.2 Literature 15 6.1.3 Post-Marketing Experience 18 6.2 Tables of Clinical Studies 18 6.3 Review Strategy 20 6.4 Good Clinical Practices (GCP) and Data Integrity 21 6.5 Financial Disclosures 21 7. Human Pharmacology 21 8. Clinical Studies 8.1 Indication #1: Prevention of rotavirus gastroenteritis caused by G1 and non-G1 types 8.1.1 Rota-023 21 8.1.2 Rota-036 61 8.1.3 Rota-004 111 8.1.4 Rota-006 146 9. Overview of Efficacy Across Trials 9.1 Indication #1: Prevention of rotavirus gastroenteritis caused by G1 and non-G1 types 9.1.1 Methods 189 9.1.2 General Discussion of Efficacy Endpoints 190 9.1.3 Study Design 193 9.1.4 Efficacy Findings 194 9.1.5 Efficacy Conclusions 206 10. Overview of Safety Across Trials 10.1 Safety Database 206 10.2 Safety Assessment Methods 207 10.3 Significant/Potentially Significant Events 214 10.4 Other Safety Findings 227 10.5 Safety Conclusions 257 11. Additional Clinical Issues 11.1 Directions for Use 257 11.2 Dose regimens and Administration 258 11.3 Special Populations 259 11.4 Pediatrics 259 3 12. Conclusions – Overall 260 13. Recommendations 13.1 Approval, Non-approval, Conditions 260 13.2 Recommendation on Post-marketing Actions 260 13.3 Labeling 263 14. Comments and questions for the applicant 264 15. Appendix 1 267 16. Applicant’s responses to comments and questions in Section 14 277 3 Executive Summary This Biologics License Application (BLA) contains efficacy, immunogenicity, and safety data TM provided by GlaxoSmithKline to support approval of Rotarix , a live, oral, monovalent rotavirus (RV) vaccine indicated for the prevention of RV gastroenteritis (GE) caused by G1 and non-G1 TM types. Rotarix is to be administered as a 2-dose series to healthy infants 6 to 24 weeks of age, with doses separated by a minimum interval of 4 weeks. The proposed release specification potency is ------- median Cell Culture Infective Dose (CCID50) per dose of live, attenuated human 6.0 RV, with an end-of-shelf-life potency of ≥ 10 CCID50 per dose. The Biologics Licensing Application (BLA) contains six Phase II trials and five Phase III trials. Two of the Phase III trials are considered pivotal efficacy studies: Rota-023, conducted in 11 Latin American countries, and Rota-036, conducted in six European countries. Rota-023 was also specifically designed and powered to evaluate the risk of definite intussusception (IS), with over TM 63,000 infants from 11 Latin American countries plus Finland receiving either Rotarix or placebo. Rota-033 was a Phase III lot-to-lot consistency study of 3 lots conducted in three Latin American countries. Rota-060, a Phase III trial evaluating the immunogenicity of routine childhood vaccines TM when co-administered with Rotarix , was conducted in the U.S. Efficacy Two Phase III studies, Rota-023 and Rota-036, are considered pivotal to the efficacy claims in this BLA. The primary objective of Rota-036 was to assess vaccine efficacy (VE) against any RV GE during the first efficacy follow-up period from 2 weeks post-Dose 2 until the end of the first RV epidemic season. The primary objective of Rota-023 was to assess VE against severe RV GE during the first efficacy follow-up period from 2 weeks post-Dose 2 until 12 months of age. Both studies were prospective, randomized, double-blinded, placebo-controlled trials. In each study, the According to Protocol (ATP) efficacy cohort was used for the primary efficacy analyses, and TM consisted of 17,867 subjects (Rotarix : 9009, placebo: 8858) in Rota-023 and 3874 subjects TM (Rotarix : 2572, placebo: 1302) in Rota-036. VE for each endpoint was calculated using the TM following formula: 1 – (attack rate in the Rotarix group ÷ attack rate in the placebo group). In Rota-036, RV GE was defined as an episode of GE in which RV other than the vaccine strain was identified in a stool sample collected no later than 7 days after GE symptom onset, while severe RV GE was defined as an episode of RV GE with a score of ≥ 11 points using the Vesikari scale. In Rota-023, the primary case definition of severe RV GE was defined as an episode of RV GE requiring hospitalization and/or rehydration therapy (equivalent to WHO plan B or C) in a medical facility. TM 6.5 The applicant demonstrated that Rotarix , at 10 CCID50 per dose, was effective in preventing naturally occurring RV GE of any grade of severity and severe RV GE during the first year of life. VE was 87.1% (95% CI: 79.6, 92.1%) against any RV GE in Rota-036. VE against severe RV GE 4 was 95.8% (95% CI: 89.6, 98.7%) in Rota-036 compared to 84.7% (95% CI: 71.7, 92.4%) in Rota- 023, suggesting geographical and/or ethnic differences in efficacy. Protection was also demonstrated against any and severe RV GE caused by circulating G1 and certain non-G1 types, as well as other clinical endpoints during the first-year, second-year, and combined (first- and second-year) efficacy follow-up periods. Immunogenicity TM Immunogenicity to Rotarix was assessed by measuring serum anti-RV IgA antibodies, considered a standard measure of immunity in most field studies and vaccine trials, at pre- and post- vaccination time points. Definitions of seropositivity and seroconversion were uniform across studies. Seropositivity was defined as an anti-RV IgA concentration ≥ 20 U/mL. Seroconversion was defined as an anti-RV IgA concentration ≥ 20 U/mL in a subject seronegative for RV pre-Dose 1. Stool samples were also collected to evaluate vaccine take, defined as anti-RV IgA seropositivity in any post-vaccination blood sample or detection of RV antigen in any post-vaccination stool sample in a RV-uninfected subject pre-vaccination. Anti-RV IgA seroconversion rates and geometric mean concentrations (GMCs) were measured in all or a pre-defined subset of subjects from all BLA studies, while vaccine take was estimated in 7 studies, including Rota-033. In each study, the ATP immunogenicity cohort was used for the primary immunogenicity analyses. TM 6.5 6.8 In studies that evaluated Rotarix at 10 CCID50 to 10 CCID50 per dose (total number of TM Rotarix subjects at these potencies in the ATP immunogenicity cohorts = 2642), 2 doses of TM Rotarix appeared immunogenic in infants, as demonstrated by post-Dose 2 anti-RV IgA seroconversion rates, GMCs, and vaccine take rates. At 1-2 months post-Dose 2, the anti-RV IgA seroconversion rate was 86.5% (95% CI: 83.9, 88.8%) in Rota-036 compared to 76.8% (95% CI: 72.4, 80.9%) in Rota-023. Similarly, 1-2 month post-Dose 2 GMC was higher in Rota-036 (197.2 U/mL; 95% CI: 175.2, 222.0 U/mL) than in Rota-023 (102.6 U/mL; 95% CI: 86.3, 122.0 U/mL). These results suggest that geographical and/or ethnic factors may impact the anti-RV IgA immune TM response to Rotarix . Safety Intussusception (IS) TM In Rota-023, the primary safety objective was to determine the safety of Rotarix with respect to IS occurring within 31 days (Days 0-30) after each dose. The safety database consisted of the Total TM Vaccinated Cohort (Rotarix : 31,673, placebo: 31,552) that was followed from Dose 1 to 1-2 months post-Dose 2. Definite IS was defined as a diagnosis of IS confirmed by intestinal invagination at surgery or autopsy, or by radiologic techniques (gas/liquid contrast enema or abdominal ultrasound). The primary safety objective was achieved if the following two criteria were met: upper limit of the 95% TM confidence interval (CI) of the risk difference (Rotarix minus placebo) for definite IS was <6/10,000 and lower limit of the 95% CI of the risk difference was < 0. An increased risk of definite IS following TM Rotarix vaccination was not observed within 31 days after any dose when the date of IS diagnosis was used to categorize cases (risk difference/10,000 = -0.32; 95% CI: -2.91, 2.18/10,000). An increased risk within 31 days was also not demonstrated in an FDA analysis that used the date of IS 7 onset to categorize cases (risk difference = -8.48/10 ; 95% CI: -2.63, 2.61/10,000). Increased risk was not observed after Dose 1 or Dose 2. Temporal clustering after either dose was also not observed. TM When pooled safety data from 8 BLA studies of subjects who received Rotarix at the proposed 6.0 licensure potency (≥ 10 CCID50 per dose; n = 36,755) were analyzed (Core Integrated Safety TM Summary [ISS] analysis), a statistically significant increased risk of IS within 31 days after Rotarix TM was not observed (Rotarix : 9 [0.024%], placebo: 7 [0.020%]; RR=1.23, 95% CI: 0.41, 3.90). Pooled TM safety data from 5 BLA studies of subjects who received Rotarix at the less-than licensure potency (< 5 6.0 10 CCID50 per dose; n = 3076) (Supplementary ISS analysis) also did not demonstrate a significantly TM TM increased risk of IS within 31 days after Rotarix (Rotarix : 1 [0.033%], placebo: 0 [0%]; LL 95% CI: 0.01). Serious adverse events - deaths A total of 118 deaths (0.158% of all study subjects) were reported throughout the course of the TM 6.0 studies. Overall death rates were 0.184% (68/36,755) in the Rotarix (≥ 10 CCID50 potency) TM 6.0 group, 0.163% (5/3076) in the Rotarix (< 10 CCID50 potency) group, and 0.158% (55/34,739) in the placebo group. In the Core and Supplementary ISS analyses for deaths, there were no significant imbalances between treatment groups in the rates of fatalities during the 31 days post- vaccination or entire study follow-up periods. For either follow-up period, there were no significant imbalances in fatalities between groups for any Medical Dictionary for Regulatory Activities (MedDRA) Preferred Term (PT). Pneumonia deaths – Rota-023 In Rota-023, an FDA analysis revealed statistically significant difference between treatment groups in the rate of subjects with pneumonia-related deaths between Dose 1 and Visit 3 (1-2 months post- TM Dose 2 or 2-4 months post-Dose 1) (Rotarix : 0.051%, placebo: 0.019%; p = 0.0354). The applicant provided a p-value of 0.054. Pneumonia-related death rates within 31 days post- TM vaccination were still higher in Rotarix compared to placebo recipients (0.022% [7/31,673] vs. 0.010% [3/31,552]). However, there were no differences between the treatment groups in rates of non-fatal pneumonia events and pneumonia hospitalizations (Dose 1 to Visit 3, within 31 days and beyond 31 days post-vaccination). Serious adverse events In the Core and Supplementary ISS analyses for severe adverse events (SAEs), there were no significant imbalances between treatment groups in the rates of subjects with at least 1 SAE during the 31 days post-vaccination or during the entire study follow-up period. In the Core ISS analysis, PTs Diarrhea, Gastroenteritis, Dehydration, and Ileus were reported significantly less during the entire TM study follow-up periods in the Rotarix group than in the placebo group. There were no significant TM imbalances for any other specific PT except Foreign body trauma (Rotarix : 11/36,755 [0.035%], placebo: 1/34,739 [0.003%]; RR = 9.11, 95% CI: 1.31, 394.8). However, all cases involved swallowing a foreign body between 48-483 days post-dose, and were assessed by the applicant as not related to vaccination. Convulsions – Rota-023 In Rota-023, a statistically significant difference between treatment groups was observed in the rate TM of PT Convulsions between Dose 1 and Visit 3 (Rotarix : 16/31,673 [0.051%], placebo: 6/31,552 [0.019%]; p = 0.034). However, when convulsion-related PTs (Convulsions, Epilepsy, Grand mal convulsion, Status epilepticus, and Tonic convulsion) were pooled in a post-hoc analysis, a TM statistically significant difference between groups was not demonstrated (Rotarix : 20/31,673 [0.063%], placebo: 12/31,552 [0.038%]; p = 0.219). Furthermore, convulsion-related episodes within TM 31 days after any dose occurred less in Rotarix recipients than placebo recipients. Among subjects who experienced a convulsion-related event within 31 days after any dose, 7 (0.022%) TM were Rotarix and 9 (0.029%) were placebo recipients. Within 43 days post-vaccination, 12 TM (0.04%) Rotarix and 9 (0.03%) placebo recipients reported a convulsion-related event. Imbalances between groups in convulsion-related PTs within 31 or 43 days post-vaccination were not observed in Rota-036. 6 Pneumonia – Rota-036 TM In Rota-036, rates of PT Pneumonia were significantly higher in the Rotarix compared to the placebo group from Dose 1 to Visit 7 (end of the second RV epidemic season) (24 vs. 4, p = 0.029). TM Of the 28 cases, only one (Rotarix group) was reported within 31 days after vaccination. CBER’s TM analysis showed that 3 cases in the Rotarix group compared to 0 in the placebo group reported PT Pneumonia within 43 days after vaccination. Furthermore, when the CBER reviewer combined the pneumonia-related PTs (Pneumonia, Bronchopneumonia, Lobar pneumonia, Pneumonia viral), TM an imbalance was still seen from Dose 1 to Visit 7 (Rotarix : 31, placebo: 7), within 31 days post- TM TM vaccination (Rotarix : 2, placebo: 0) and within 43 days post-vaccination (Rotarix : 5, placebo: 0). Imbalances between groups in pneumonia-related PTs within 31 or 43 days post-vaccination were not observed in Rota-023. Unsolicited adverse events (non-SAEs) In the Core and Supplementary ISS analyses for unsolicited AEs 31 days post-vaccination, there were no significant imbalances between groups in the rates of subjects with at least 1 AE of any intensity or Grade 3 intensity after any dose. In the Core ISS analysis, there were small but TM statistically significant increases in Rotarix compared to placebo recipients in rates of PTs Irritability (11.4% vs. 8.7%) and Flatulence (2.2% vs. 1.3%). However, no significant imbalances in Grade 3 Irritability and Flatulence were observed. In the Supplementary ISS analysis, there was a TM statistically significant increase in rates of PT Bronchitis in Rotarix compared to placebo recipients TM (1.85% vs. 0.74%, RR=2.39, 95% CI: 1.27, 4.90%). Grade 3 Bronchitis occurred in 6 Rotarix compared to 0 placebo recipients. The applicant stated that this imbalance was driven by an TM imbalance of Bronchitis in Rota-006. FDA calculated a total of 44 (3.9%) Rotarix recipients (< 6.0 10 CCID50 groups) compared to 10 (1.8%) placebo recipients in Rota-006 who reported PT TM Bronchitis during Days 0 to 30 post-vaccination. Grade 3 Bronchitis occurred in 1 Rotarix TM compared to 0 placebo recipients. In Rota-006, the rate of any Bronchitis in the Rotarix group receiving the licensure potency was higher than in the placebo group during this same interval TM (3.7% vs. 1.8%); no Grade 3 Bronchitis was reported in this Rotarix group. In the Core ISS TM analysis, when PTs Bronchitis and Bronchitis acute were combined, 116 (2.3%) Rotarix recipients compared to 45 (1.6%) placebo subjects reported an AE. Grade 3 AE rates were comparable TM (Rotarix : 0.16%, placebo: 0.14%). Solicited adverse events In the Core and Supplementary ISS analyses for solicited symptoms 8 days (Days 0-7) post- vaccination, there were no significant imbalances in rates of fever, irritability, loss of appetite, TM vomiting, or diarrhea, of any severity or Grade 3 severity, between the Rotarix and placebo groups after any dose. The exception was Grade 3 cough/runny nose after any dose in the Core ISS analysis TM (Rotarix : 3.6%, placebo: 3.2%, RR=1.41, 95% CI: 1.01, 1.99). However, imbalances in rates of cough/runny nose after each dose were not observed. Shedding and Transmission Post-vaccination RV antigen shedding in stools was evaluated in all or a subset of subjects from 7 TM BLA studies. In all studies (total number of Rotarix subjects in the ATP immunogenicity cohorts = 1086), samples were collected on Day 7 after each dose, while in 4 studies, samples were also collected on Day 15 post-dose. In addition, 4 studies collected samples at 30 days post-Dose 1 (pre-Dose 2), while 4 studies collected samples at 60 days post-Dose 1 (pre-Dose 2). TM 6.5 6.8 Among Rotarix treatment groups from studies that administered vaccine at 10 CCID50 to 10 CCID50 per dose, post-Dose 1 RV antigen shedding ranged from 50.0% to 80.0% of subjects at Day 7, 19.2% to 64.1% at Day 15, 0% to 24.3% at Day 30, and 0% to 2.6% at Day 60. The highest rates 7 of post-Dose 1 shedding at Days 7, 15, and 30 occurred in subjects from Rota-007, a Phase II study conducted in Singapore. The applicant stated that these results may be due to a population effect or older age at Dose 1 (median = 13 weeks) when maternal antibodies known to have an TM impact on RV immune response have already declined. Among the same Rotarix treatment groups, post-Dose 2 shedding ranged from 4.2% to 18.4% at Day 7, 0% to 16.2% at Day 15, and 0% to 1.2% at Day 30. Shedding at Day 45 post-Dose 2, monitored only in Rota-033, was 0%. Highest post-Dose 2 shedding rates at Days 7 and 15 were also in subjects from Rota-007. TM 6.5 In 2 BLA studies that administered Rotarix at 10 CCID50 per dose, an estimated 25.6% to 26.5% of subjects shed live RV at Day 7 post-Dose 1. In addition, data from 4 other studies combined demonstrated that among RV antigen-positive samples, live RV was detected in fewer TM samples from Rotarix vaccinated subjects than samples from wild-type RV GE episodes (14.6% vs. 68.6%) TM Transmission of Rotarix was not formally evaluated in any of the BLA studies. Co-Administration with Other Childhood Vaccines TM Concomitant administration of other routine childhood vaccines with Rotarix or placebo was allowed in 10 of the 12 BLA studies. Only one study (Rota-014, Phase II, South Africa; n = 447) allowed concomitant administration of oral poliovirus vaccine. Only Rota-060 was specifically designed to evaluate non-inferiority of immune responses to diphtheria, tetanus, pertussis, hepatitis B, poliovirus, Haemophilus influenza type b (Hib), or S. TM pneumoniae antigens when these routine vaccines were co-administered with Rotarix . All study subjects received 3 doses each of Pediarix® (DTaP-HepB-IPV), Prevnar® (pneumococcal 7-valent TM conjugate vaccine), and ActHIB®. In the co-administration group, Rotarix was administered with TM the first two routine vaccine doses, while in the separate administration group, Rotarix was administered one month after routine vaccine Doses 1 and 2. Antibody responses to diphtheria, tetanus, pertussis (PRN, FHA, PT), hepatitis B (HBs), poliovirus (types 1, 2, 3), Hib (PRP), and S. pneumoniae (serotypes 4, 6B, 9V, 14, 18C, 19F, 23F) antigens were measured one month after Dose 3 of routine vaccinations. Non-inferiority criteria were based on comparisons of seroprotection rates (diphtheria, tetanus, hep B, Hib, polio) and GMCs (pertussis, S. pneumoniae) between treatment TM groups. Non-inferiority criteria were met for all antigens, indicating that co-administration of Rotarix with routine childhood vaccines did not impair the immune responses to any of these vaccine antigens. Conclusion TM 6.5 Rotarix at a potency of 10 CCID50 per dose was effective in preventing RV GE of any grade of severity and in preventing severe RV GE caused by naturally-occurring RV strains during the first year of life across heterogeneous geographical populations. Protection against any and severe RV GE was also demonstrated against circulating G1 and certain non-G1 types that are similar in distribution in the TM U.S. Co-administration of Rotarix with other routine vaccines in the U.S. did not cause interference of TM the immune response to each of these vaccine antigens. Rotarix had no increased risk of intussusception. However, increases in pneumonia-related deaths and convulsion-related SAEs were TM observed in Rotarix compared to placebo recipients from Dose 1 to Visit 3 in Rota-023, although the difference in pneumonia-related deaths occurring within 31 days post-vaccination was smaller. Rates of TM bronchitis within 31 days post-vaccination were also generally higher in Rotarix recipients, most notably in Rota-006. 8 Recommendation: The reviewer recommends that Rotarix be approved for use in infants 6 to 24 weeks of age. As part of the pre-BLA agreement, the applicant will conduct a prospective US post-licensure observational safety study that will be adequately powered to evaluate the risk of intussusception. Other measured outcomes will include deaths from all causes, hospitalizations due to acute lower respiratory tract infections (including pneumonia), convulsions, and Kawasaki disease. 4 Significant Findings from Other Review Disciplines 4.1 Chemistry, Manufacturing and Controls (CMC) Description of the Product GSK Biological’s candidate oral live attenuated human RV (HRV) vaccine, Rotarix®, was developed from the 89-12 candidate vaccine strain, a G1P[8] strain isolated from a naturally infected 15-month study subject (subject #----, 1988-89 RV season, Cincinnati, OH) and attenuated by 33 passages in 48, 49, 50 African Green Monkey cell culture. The 89-12 vaccine, licensed by Avant Immunotherapeutics (US), was subsequently sub-licensed by GSK Biologicals in 1997, after which time several process changes were implemented to obtain a cloned 89-12 strain at passage --, referred to as the RIX4414 vaccine strain and subsequently used as GSK Biological’s candidate HRV vaccine. GSK Biological’s candidate HRV vaccine used for clinical testing was prepared by reconstituting the lyophilized preparation with separately supplied liquid calcium carbonate based buffer prior to oral administration in subjects. The composition of 1 mL of Rotarix is shown below in Table 3. Table 3. Composition of Rotarix* Ingredient Quantity per 1 mL Active substance 6.0 Human RV, live attenuated, RIX4414 strain At least 10 CCID50** Excipients Lyophilized with active substance: - Sucrose ---- - Dextran ----- - Sorbitol ------- - Amino acids ----- - Dulbecco’s Modified Eagle Medium -------- In liquid diluent: - Calcium carbonate ----- - Xanthan ------ - Sterile water q.s. ad 1 mL *Data extracted from Clinical Overview, pg. 16 **CCID50 = median Cell Culture Infective Dose (quantity of virus causing infection in 50% of exposed cells) The CMC reviewer did not identify any major manufacturing issues and control problems. Two 6.0 comments raised by the reviewer related to the applicant’s choice of ≥ 10 CCID50 as the end of shelf-life potency and ----- CCID50 as the proposed specification potency. The applicant stated that 5.6 6.6 clinical lots from a Phase II trial (Rota-006) containing 10 CCID50and 10 CCID50 were chosen to select the final dose potency. The CMC reviewer questioned these lots, rather than the Phase III lots, were not chosen. The reviewer also raised the question as to why the applicant -------------------- 9 ------------------------------------ rotavirus titer allowable per vaccine dose. At the time of this review, these potency-related issues were still being discussed and further investigated by the review team. The bioassay reviewer did not identify statistical bioassay related issues that may preclude the BLA submission from being approved by the agency. Please refer to CBER’s CMC and bioassay reviews for more details. 4.2 Animal Pharmacology/Toxicology One single dose combination repeat dose toxicity study was submitted in support of the BLA. In this study, 21-day old ------------ rats were given 4 doses of rotavirus vaccine orally. The four doses used exceeded the number of injections intended for use in the clinic, with dosing intervals of 2 weeks. The full human dose of 0.5 ml of vaccine was used in the study. Four groups of rats were 6.7 studied: saline group, CaCO3 group, human rotavirus strain RIX 4414 at 10 ffu and CaCO3 group, 6.1 and RIX 4414 at 10 ffu. No treatment-related effects were observed on the following endpoints: clinical signs, mortality, body weight, food intake, ophthalmology, body temperature, coagulation, macroscopic findings upon necropsy, histopathology and clinical chemistry. Of note, no histopathological changes were found in the intestinal villi such as epithelial syncytia and no intracytoplasmic eosinophilic inclusions in the ileum. Low seroconversion rates of 10% and 20% were observed in the study population. Variable viral shedding was observed in rats given the rotavirus strain. Please refer to CBER’s toxicology review for more details. 5 Clinical and Regulatory Background 5.1 Disease or Health-Related Condition(s) Studied and Available Interventions Epidemiology Rotavirus (RV) infection is the leading cause of severe acute gastroenteritis (GE) in infants and young children worldwide. In the United States, RV infection causes 2.7 million GE episodes, over 400,000 outpatient visits, and up to 70,000 hospitalizations and 60 deaths annually in children 1, 2 under 5 years of age. RV is transmitted primarily by the fecal-oral route through close person-to-person contact and 3 4 through fomites. Respiratory droplets may be another mode of transmission. RV disease occurs from winter to spring in temperate climates, and year-round in tropical and 5, 6, 7, 8, 9 10, 11, 12 subtropical areas. In the US, disease occurs from November to March. In North America and Europe, most RV infections occur in the first and second years of life, while severe GE 1, 13, 14 occurs mainly in 3 to 35 month-old children. Subsequent infections usually result in much 13 milder disease. Virology/Molecular Epidemiology RV is classified according to a binary system based on two protein types: G (glycoprotein) types and P (protease-cleaved protein) types. Ten G types and 11 P types have been isolated from humans. These human RVs can further be classified into two major genetically distinct groups: Wa 10 genogroup and DS-1 genogroup. The Wa genogroup includes most human G1, G3, G4, and G9 strains, while the DS-1 genogroup is comprised mainly of G2 strains. Worldwide, 88.5% of childhood RV diarrhea is caused by G types 1 to 4 associated with P types 15, 16, 17, 18, 19, 20 P[8] and P[4]. In the 1990’s, G9 type appeared to emerge as the fifth most common 21,22, 23, 24, 25, 26, 27, 28, 29 type, with mostly G9P[8] strains circulating in the US and Europe. In North America, Europe and Australia, G1P[8], G2P[4], G3P[8], and G4P[8] represent over 90% of RV 20 infections. In the US, the yearly prevalence of G1, G2, G3, and G4 types have been 70%, 6-15%, 20, 21, 24, 30 20 1-8%, and 0-2%. These figures are similar to those of other developed countries. Other 20, 22, 23, 26, 31 uncommon types such as G1P[4] and G2P[8] also circulate in these countries. As shown in Table 4 below, distribution of prevalent RV types are comparable between North America, Latin America, and Europe, areas where the HRV vaccine efficacy has been demonstrated. Table 4. Distribution of predominant human RV G types by region, 1973 to 2003* Region N G1 G2 G3 G4 Other types Latin America 2,950 57.5% 18.3% 4.4% 8.8% 11.0% Europe 17,475 69.4% 10.2% 3.5% 15.5% 1.4% North America 2,892 73.7% 11.0% 10.6% 2.7% 2.0% *Data extracted from Clinical Overview, pg. 11; source – reference #20 Immunity RV infection in children induces serum and intestinal antibody responses that result in protection against diarrhea, especially severe diarrhea, upon subsequent infection. Serum antibodies consist of specific IgM, followed by anti-RV IgA and IgG. Small intestinal antibodies are predominantly IgA. Specific serum IgA antibodies are generally considered the standard measure of immunity in most field studies and vaccine trials. While the humoral immune response is considered the key mechanism of protection, human and animal studies have also demonstrated that cell-mediated immunity may play a more prominent role in 32, 33, 34 the RV immune response. However, mice studies indicate that although RV-specific cytolytic T 35 cells help to resolve infection, they are less protective against reinfection than antibody. 36 The G (VP7) and P (VP4) proteins are the two main targets of neutralizing antibodies. However, it is likely that a protective immune response involves all structural and non-structural proteins of RV. In children 0 to 24 months old, RV infections during the first life protect against severe RV reinfection during the second year of life, even when the second infection is caused by a different G 37 type from the first. In most cases, homotypic immunity (immunity against the same RV type) develops after the first infection, with heterotypic immunity (immunity against different RV types) 37 developing with successive RV infections. Even asymptomatic infection during the first year of life induces the same level of protection as symptomatic infection, thereby allowing reasonable assumption that vaccines that cause asymptomatic RV infection may provide adequate protection. 37, 38, 39, 40 Clinical disease After a 2 to 4 day incubation period, abrupt onset of fever, abdominal distress, diarrhea and vomiting occur. Diarrheal stools are typically loose and water and occur frequently; mucus is found less often, with blood being rare. Symptoms usually last 3 to 9 days, and can lead to severe dehydration. Untreated severe RV GE in infants can be rapidly fatal. Viral shedding can be measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase-polymerase chain reaction (RT-PCR), and can persist for as long as 57 days after disease onset in 41, 42 immunocompetent hosts.