Two-dose regimen for pre-exposure prophylaxis
The two-dose regimen (on Day 0, and Day 7) was assessed in two phase 3 studies.
In one observer-blind, randomized, controlled, multicenter study conducted in Thailand (Study 2), RVNA responses after 2 doses of IMOVAX RABIES were compared to RVNA responses after 3 doses of IMOVAX RABIES. In this study, 100 healthy participants 18 years of age and older (including 2 participants 65 years of age and older), and 100 participants 1 year through 17 years of age received a 3-dose pre-exposure prophylaxis regimen of IMOVAX RABIES. A key secondary objective of the study was to demonstrate in the pooled participants (from 1 year through 17 years of age and 18 years of age and older), the noninferiority of a 2-dose pre-exposure prophylaxis regimen of IMOVAX RABIES (on Day 0, and Day 7) at Day 28 compared to the 3-dose pre-exposure prophylaxis regimen of IMOVAX RABIES (on Day 0, Day 7, and Day 28) at Day 42 in terms of the percentage of participants with an RVNA titer ≥ 0.5 IU/mL. The analysis was done in the per protocol analysis set (PPAS) with data from Day 28 and Day 42 contributed from the same participants, and with the prespecified noninferiority margins of -10% and -5%.
At Day 28 (after 2 doses of IMOVAX RABIES), 98.8% of participants had an RVNA titer ≥ 0.5 IU/mL. At Day 42 (after 3 doses of IMOVAX RABIES), 100% participants had an RVNA titer ≥ 0.5 IU/mL. The difference in the percentage of participants who achieved an RVNA titer ≥ 0.5 IU/mL was -1.3% [95% confidence interval (CI): -4.4; 1.3]. As the lower bound of the 95% CI of this difference (-4.4%) was greater than the prespecified noninferiority margins of -10% and -5%, noninferiority of the 2-dose pre-exposure prophylaxis regimen at Day 28 to the 3-dose pre-exposure prophylaxis regimen at Day 42 was demonstrated.
In an open-label, randomized, controlled, multicenter study (Study 1) conducted in the Philippines, 228 healthy participants (including 101 participants from 2 years through 17 years of age and 127 participants 18 years through 52 years of age) were randomized to receive the 2-dose pre-exposure prophylaxis regimen of IMOVAX RABIES and 115 healthy participants (including 46 participants from 2 years through 17 years of age and 69 participants 18 years through 59 years of age) were randomized to receive a 3-dose pre-exposure prophylaxis regimen of IMOVAX RABIES. One year later, 200 participants from the 2-dose pre-exposure prophylaxis group and 107 participants from the 3-dose pre-exposure prophylaxis group received two doses of IMOVAX RABIES 3 days apart (on Day 0 and Day 3) to mimic a post-exposure prophylaxis regimen without actual rabies exposure (simulated post-exposure prophylaxis).
The primary objective of the study was to demonstrate noninferiority of a 2-dose pre-exposure prophylaxis regimen of IMOVAX RABIES (on Day 0 and Day 7) at Day 21 compared with the 3-dose pre-exposure prophylaxis regimen of IMOVAX RABIES (on Day 0, Day 7 and Day 28) at Day 35, in terms of the percentage of participants with an RVNA titer ≥ 0.5 IU/mL. The analysis was done in the PPAS with the prespecified noninferiority margin of -5%.
At Day 21, 96.7% of participants who received the 2-dose pre-exposure prophylaxis regimen of IMOVAX RABIES had an RVNA titer ≥ 0.5 IU/mL. At Day 35, 100% participants who received the 3-dose pre-exposure prophylaxis regimen of IMOVAX RABIES had an RVNA titer ≥ 0.5 IU/mL. Noninferiority was not demonstrated as the difference in the percentage of participants who had an RVNA titer ≥ 0.5 IU/mL threshold was ‑3.3% (95% CI: -6.8; 0.5) and the lower bound of the 95% CI was below the prespecified noninferiority margin (‑5%). All participants 2 years through 17 years of age who received the 2-dose pre-exposure prophylaxis regimen of IMOVAX RABIES had an RVNA titer ≥ 0.5 IU/mL at Day 21.
One year later, following the simulated post-exposure prophylaxis, 100% of participants primed with either a 2-dose or 3-dose pre-exposure prophylaxis regimen of IMOVAX RABIES had an RVNA titer ≥ 0.5 IU/mL at 7 and 14 days after the first simulated post-exposure prophylaxis injection, which demonstrated an anamnestic response.