Benzinga | May 11, 2021 09:12AM EDT

Phio Pharma Reports New In Vivo Data Showing PH-762 'Significantly' Enhanced Antitumor Efficacy Of HER2-Targeted CAR-T Cells In Solid Tumors

Phio Pharmaceuticals Corp. (NASDAQ:PHIO), a biotechnology company developing the next generation of immuno-oncology therapeutics based on its proprietary self-delivering RNAi (INTASYL(tm)) therapeutic platform, today announced positive new in vivo data showing that PH-762 significantly enhanced the antitumor efficacy of HER2-targeted CAR-T cells (HER2CART) in solid tumors. Compared to untreated HER2CART cells, HER2CART cells treated with PH-762 showed a statistically significant and durable inhibition of tumor growth. These data, using a HER2-targeted CAR-T cell product against a HER2-expressing ovarian cancer xenograft model, provide proof-of-concept for the application of PD-1 checkpoint silencing with INTASYL in CAR-T cells prior to adoptive cell therapy to enhance the therapeutic efficacy of CAR-T cell therapy in solid tumors.

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"The in vivo data announced today further support advancing the development of PH-762 into the clinic as a viable approach to improve various forms of T cell based immunotherapy. These data are especially impressive considering that to date CAR T-cell therapy effectiveness in solid tumors has been disappointing and the use of additional genetic engineering to address these issues has proven challenging and costly. Indeed, in a recent clinical study it was shown that CRISPR-Cas9 mediated PD-1 disruption resulted in low efficiency, namely an editing efficiency of less than 6% and a median disruption of PD-1 expression of less than 50% in the edited T cells. This compares sharply with our results where we show that our INTASYL compound, PH-762, achieves PD-1 silencing efficiency of ~90% in nearly 100% of the HER2CART cells used in this study," stated Dr. Simon Fricker, Phio's VP of Research. "In addition, these results are achieved by merely adding PH-762 to the HER2CART cell culture media, without the need for cell delivery vehicles or vectors, and without negative impact on cell growth/survival. In a prior presentation we also showed how PH-762 can improve the tumor cell killing activity of another adoptive cell therapy platform, namely tumor infiltrating lymphocytes. Taken together, you can start to see the full picture of the potential advancement that INTASYL could provide in adoptive cell therapy."

In this study the Company assessed the potential of PH-762, a PD-1 targeting INTASYL compound, to enhance the therapeutic efficacy of HER2CART cells in the treatment of a subcutaneous HER2-expressing SKOV3 model of human ovarian cancer in mice. On-target silencing of PD-1 in vitro was demonstrated in a dose associated manner in activated HER2CART cells, without significant impact on viability, and resulted in an enrichment of CD8+ and CD25+ cells. Analyses of PH-762-treated HER2CART cells isolated from tumors suggest that PH-762 enhances CAR-T function through multiple mechanisms including enhanced efficiency, degranulation, decreased suppressive potential, and promotion of memory/stem populations.

These data were presented today during the 24th Annual Meeting of the ASGCT in a poster titled "INTASYL PH-762 Self-Delivering RNAi Targeting PD-1 Enhances the Therapeutic Efficacy of Systemically Administered HER2-Targeted CAR-T Cells in a SKOV3 Model of Human Ovarian Adenocarcinoma in NCG Mice". An archived version of the poster presentation will be made available on the "Investors -- Events and Presentations" section of the Company's website (click here).