Mateon Announces New Preclinical Data Demonstrating Enhanced Tumor Immune Responses when CA4P is Given in Combination with Checkpoint Inhibitors

· CA4P and checkpoint inhibitor combination nearly doubles amount of tumor necrosis

SOUTH SAN FRANCISCO, Calif., Jan. 08, 2018 (GLOBE NEWSWIRE) — Mateon Therapeutics, Inc. (OTCQX:MATN), a biopharmaceutical company developing investigational drugs for the treatment of orphan oncology indications, today announced new preclinical data further characterizing the improved anti-tumor immune response observed when animals are treated with CA4P in combination with anti-CTLA-4 antibodies.

The new findings show that treatment with the combination of CA4P and an anti-CTLA-4 antibody nearly doubles the amount of tumor necrosis (mean = 63.9%) compared to treatment with an anti-CTLA-4 antibody alone (32.8%), CA4P alone (37.3%) or vehicle control (25.8%) in a preclinical CT-26 mouse colon cancer model using immunohistochemistry analyses.  Results from these analyses confirmed previously announced findings showing that treatment with CA4P and an anti-CTLA-4 antibody resulted in increased overall median numbers of tumor infiltrating CD8+ T lymphocytes. The new preclinical data also showed that the distribution of these beneficial CD8+T lymphocyte cells was observed throughout the tumor – in both the tumor rim and tumor core. 

“These new data further show the promise of CA4P to stimulate the immune system and enhance the efficacy of checkpoint inhibitors,” said William D. Schwieterman, M.D., President and Chief Executive Officer of Mateon Therapeutics.  “We are excited that CA4P, when combined with a checkpoint inhibitor, shows dramatic increases in tumor necrosis which are clearly correlated with an increased immunologic response, more tumor regressions and increased overall survival.  Given these new findings, the large clinical safety database for CA4P, and the need for new therapies for the many patients who have not responded to checkpoint inhibitor therapy, we believe CA4P has great promise for use with these immuno-oncology agents.”

About Checkpoint Inhibitors

Anti-CTLA-4 antibodies stimulate a patient’s immune system by blocking immunosuppression and include the approved anti-cancer drug Yervoy®.  Mateon’s investigational drug CA4P stimulates a patient’s immune system in a different but complementary manner – by inducing immediate, rapid and extensive tumor cell necrosis. Utilizing these two different but complementary immune-stimulating approaches simultaneously has the potential to improve patient outcomes for the majority of cancer patients that do not respond adequately to therapy with checkpoint inhibitors alone.

About CA4P With Checkpoint Inhibitors

Mateon previously reported data from a CT-26 colon cancer animal model showing that combination treatment with CA4P and an anti-CTLA-4 antibody 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 and also indicating a heightened immunologic response to the tumor in the presence of the two-drug combination. Importantly, treatment with both CA4P and an anti-CTLA-4 antibody 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 programs in acute myeloid leukemia and immuno-oncology. 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.


Mateon Therapeutics, Inc.
Matthew M. Loar 

JPA Health Communications
Nic DiBella