Overview of the Multi-Virus Prevention Study Open-Label Preliminary Data
On December 11, 2021, the Company announced preliminary data from the open-label portion of its ongoing Phase 2 two part multicenter, randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of posoleucel for the prevention of six viral infections – AdV, BKV, CMV, EBV, HHV-6 and JCV. The Phase 2 open-label portion of this study is enrolling 25 high-risk allo-HCT patients. Patients receive up to seven biweekly posoleucel infusions and are tested for viremia by polymerase chain reaction (PCR) on a weekly basis against all six viruses over a period of 14 weeks. Following this dosing period, patients receive follow-up through Week 26.
At the time of the data cut-off for this preliminary analysis, 23 high-risk allo-HCT patients received at least a single dose of posoleucel, including 13 patients who had completed through Week 14, one patient who discontinued the study and nine patients whose evaluation for the primary endpoint is ongoing. Of these patients, 14 (61%) received cells from haploidentical donors, six (26%) from mismatched unrelated donors, two (9%) from matched unrelated donors with T cell depletion or with lymphopenia, and one (4%) from umbilical cord blood.
In the preliminary analysis, high-risk allo-HCT patients receiving posoleucel experienced no end-organ disease and had rates of clinically significant viral infections substantially lower than the expected rate estimated through an analysis of peer-reviewed published data and electronic medical record reviews.
The primary study endpoint is the number of new onset clinically significant infections or end-organ disease through Week 14. Among the 23 patients who received at least a single dose of posoleucel, only three of 138 possible clinically significant infections from these six common and life-threatening viruses were observed up to 14 weeks. Three out of 23 patients experienced one clinically significant viral infection each. Specifically, two patients initiated preemptive CMV treatment with valganciclovir following withdrawal of letermovir, and one patient started rituximab for EBV in the setting of receiving high-dose steroids.
Repeat posoleucel dosing was generally well-tolerated, with no unanticipated safety signals. The observed rates and severity of graft versus host disease did not exceed those expected in this high-risk allo-HCT patient population. Two (9%) treatment-related serious adverse events were reported.
The Company plans to advance from the Phase 2 open-label study into a Phase 3 registrational trial in the first half of 2022, following FDA review of the final protocol.
This Form 8-K contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, statements regarding the Company’s development and regulatory status of our product candidates, the planned conduct of its preclinical studies, and clinical trials and its prospects for success in those studies and trials, and its strategy, business plans and focus. The words “may,” “will,” “could,” “would,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “project,”