OncoTherapy Science : Announcement of the Presentation of Interim Results for Phase I Clinical Study of a Combination of OTSGC-A24 and Immune Checkpoint Inhibitor in Patients with Gastric Cancer

OncoTherapy Science, Inc.

September 13, 2022

Announcement of the Presentation of Interim Results for Phase I Clinical Study of a Combination of OTSGC-A24 and Immune Checkpoint Inhibitor

in Patients with Gastric Cancer

OncoTherapy Science, Inc. (President & CEO: Junichi Shimada; hereinafter, "OncoTherapy") today announces that interim results for Phase I clinical study of a combination of OTSGC-A24 and nivolumab were presented by a poster entitled "da VINci: Safety and efficacy of the OTSGC-A24 vaccine and nivolumab in metastatic gastric cancer" at European Society for Medical Oncology Congress 2022 (Paris, France) on September 12, 2022 (CET).

This is an investigator-initiated study conducted at National University Hospital (NUH) since 2019, and OncoTherapy has provided the study drug OTSGC-A24 as a collaborator.

OTSGC-A24 is the cocktail peptide vaccine product which contains multiple peptides targeting the tumor-specific antigens that are highly expressed in gastric cancer (GC). Each peptide contained in this cocktail is identified through cancer genome analysis and expected to induce strong cytotoxic T lymphocyte (CTL) response. Phase I/II clinical study of OTSGC-A24, which is a single agent for refractory GC, was conducted in Singapore, Korea and Japan and had been completed with favorable results on safety and immune reactivity.

[Summary of the presentation]

The aim of this study is to evaluate the safety and efficacy of the combination of OTSGC- A24 and immunotherapy in the patients (pts) with unresectable or metastatic GC. Total 18 HLA-A*24:02 subtype pts with unresectable/advanced GC have been enrolled in this study. No significant safety concerns were observed. Most frequent adverse event was injection site reactions, fatigue and rush (27.8% in 5 out of 18 pts respectively). In terms of efficacy, 3 pts (16.7%) had partial response (PR) and 6 pts (33.3%) had stable disease (SD). The median progression-free survival (PFS) was 1.7 months1 and median overall survival (OS) was 3.6 months1. Of note, for the patients with SD or PR, the median PFS was 13.1 months1 and median OS was 18.6 months.

These results suggest that acceptable safety profile and clinical response of a combination of OTSGC-A24 and nivolumab may provide beneficial effect for a maintenance therapy for pts with unresectable or metastatic GC.

1 The data in the abstract was updated at the time of poster presentation as follows.

• Median PFS and OS were updated from 1.7 to 1.64 months and from 3.6 to 5.98 months, respectively.
• Median PFS at the pts with SD or PR was also updated from 13.1 to 13.50 months.

The abstract has been published online in ESMO website.

https://cslide.ctimeetingtech.com/esmo2022/attendee/confcal_2/presentation/list?q=da+vinci

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