On December 5, 2017 Mateon Therapeutics, Inc. (OTCQX:MATN), a biopharmaceutical company developing investigational drugs for the treatment of orphan oncology indications, reported 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 (Press release, Mateon Therapeutics, DEC 5, 2017, View Source [SID1234522393]). 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).
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"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.