IO Biotech (NASDAQ:IOBT) on Monday released topline results from the pivotal Phase 3 trial of its investigational, immune-modulatory, off-the-shelf therapeutic cancer vaccine, Cylembio (imsapepimut and etimupepimut, adjuvanted).
The trial evaluated Cylembio in combination with Merck & Co Inc’s (NYSE:MRK) Keytruda (pembrolizumab), vs. pembrolizumab alone as a first-line treatment for unresectable or metastatic (advanced) melanoma.
In the study, Cylembio plus pembrolizumab demonstrated clinical improvement in progression-free survival compared to pembrolizumab alone, but statistical significance was narrowly missed on the primary endpoint.
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The randomized, open-label study enrolled 407 patients. Patients received either Cylembio in combination with pembrolizumab (n=203) or pembrolizumab alone (n=204).
The early and sustained separation of PFS curves demonstrated an improvement with a hazard ratio of 0.77.
Based on an intent-to-treat analysis, patients in the study treated with Cylembio in combination with pembrolizumab achieved 19.4 months of median progression-free survival compared to 11.0 months in patients treated with pembrolizumab alone.
Although not yet mature, a trend toward an improvement in overall survival was also observed; the company expects OS to mature over the next six to nine months.
Improvement in PFS was achieved across virtually all subgroups, with a profound effect in patients with PD-L1 negative tumors treated with Cylembio plus pembrolizumab (n=67) compared to patients treated with pembrolizumab monotherapy (n=63), with mPFS of 16.6 months vs. 3.0 months, respectively.
Additionally, in a post hoc analysis of patients enrolled in this study without prior anti-PD-1 treatment (n=371), patients treated with Cylembio plus pembrolizumab achieved improvement in PFS compared to patients treated with pembrolizumab monotherapy, with mPFS of 24.8 months vs. 11.0 months, respectively.
The combination was well tolerated, with no new safety signals observed. Injection site reactions, transient and resolved on treatment, were the most commonly reported adverse events in the combination arm, with 56% of patients receiving Cylembio plus pembrolizumab reporting an event.
IO Biotech plans to meet with the U.S. Food and Drug Administration (FDA) this fall to discuss the totality of data and determine next steps for submitting a Biologics License Application (BLA) for treating advanced melanoma.
Last year, Merck discontinued the vibostolimab and pembrolizumab coformulation arm of the Phase 3 KeyVibe-010 trial of coformulation of vibostolimab and Keytruda (pembrolizumab) compared to Keytruda alone as adjuvant treatment for patients with resected high-risk melanoma.
A higher discontinuation rate of all adjuvant therapy by patients was observed in the coformulation arm versus the Keytruda-only arm, primarily due to immune-mediated adverse experiences. Thus, the trial was unlikely to achieve a statistically significant improvement in RFS.
Price Action: IOBT stock is trading lower by 10.5% to $1.621 at last check Monday.
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