Mateon Announces Preclinical Data Indicating Enhanced Tumor Immune Response Of CA4P With Checkpoint Inhibitor

• Addition of CA4P simultaneously reduces tumor volume and increases tumor white blood cells, T Cells and cytotoxic T Cells compared to anti-CTLA-4 monotherapy
• Preliminary data suggest immuno-oncology applications for drug candidate

(GLOBE NEWSWIRE) -- Mateon Therapeutics, Inc. (OTCQX:MATN), a biopharmaceutical company developing investigational drugs for the treatment of orphan oncology indications, today announced new preliminary data in a mouse model of colon cancer indicating that reductions in tumor volume after treatment with CA4P and anti-CTLA-4 combination therapy are associated with an enhanced immune response. CA4P induces immediate, rapid and extensive tumor cell necrosis which can stimulate the immune system, while antibodies to CTLA-4 stimulate the immune system through a different mechanism, by blocking immunosuppression (which is the same mechanism used by the approved drug marketed under the trade name Yervoy®).

“We are excited about the possibility of using CA4P to improve patient responses to checkpoint inhibitors, which have shown significant but nevertheless limited therapeutic benefits as monotherapy,” said William D. Schwieterman, M.D., President and CEO of Mateon Therapeutics. “While the direct clinical benefits of CA4P alone as an anti-cancer agent are limited, these initial data indicate the promise of this agent to stimulate the immune system and enhance the efficacy of checkpoint inhibitors – an exciting and rapidly emerging field of oncology where our unique approach may offer a distinct advantage.”

Mateon previously reported data from a CT-26 colon cancer animal model showing that combination treatment with CA4P and anti-CTLA-4 causes large reductions in tumor volume and statistically significant improvements in survival when compared to anti-CTLA-4 alone, CA4P alone, or vehicle control. Similar anti-tumor effects were observed when this combination was studied in an EMT-6 mammary tumor animal model. The CT-26 model was repeated for the studies reported today, again showing large reductions in tumor volume with combination therapy. This repeat study also captured additional data on immune response, with preliminary data showing increases in the median number of tumor-associated white blood cells (WBC’s) (69.2K vs. 39.0K vs. 16.7K for CA4P plus anti-CTLA-4, anti-CTLA-4 alone and vehicle control, respectively), T cells (5.2K vs. 1.6K vs. 1.8K), and effector cytotoxic CD8+ T Cells (2.0K vs. 0.8K vs. 0.5K), indicating a heightened immunologic response to the tumor in the presence of the two-drug combination. Importantly, treatment with both CA4P and anti-CTLA-4 generally maintains an elevated tumor-associated median effector T cell/regulatory T cell ratio, which also indicates a heightened immune response. Work to further characterize the immune response seen with the combination is ongoing.

About Mateon
Mateon Therapeutics, Inc. is a biopharmaceutical company developing investigational drugs for the treatment of orphan oncology indications, with its lead program in acute myeloid leukemia and myelodysplastic syndromes. Mateon is committed to leveraging its product development expertise and intellectual property to bring improved and medically necessary new therapies to cancer patients worldwide.

Safe Harbor Statement
Certain statements in this news release, including, but not limited to, those concerning the pre-clinical data on the combination of CA4P with checkpoint inhibitors, the potential significance of this data and its relation to other clinical and pre-clinical studies are considered "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. They can be affected by inaccurate assumptions Mateon might make or by known or unknown risks and uncertainties, including, but not limited to: the sufficiency of the Company’s cash resources to continue in business and to conduct and complete future clinical and pre-clinical trials; the uncertainties as to the future success of ongoing and planned clinical trials; and the unproven safety and efficacy of products under development or that may be developed in the future. Consequently, no forward-looking statement can be guaranteed, and actual results may vary materially. Additional information concerning factors that could cause actual results to materially differ from those in the forward-looking statements is contained in Mateon’s reports to the Securities and Exchange Commission, including Mateon’s reports on Forms 10-Q, 8-K and 10-K. However, Mateon undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise.

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