Threshold Pharmaceuticals Announces First Patient Dosed in Immunotherapy Clinical Trial

Threshold Pharmaceuticals, Inc. recently announced that the University of Texas MD Anderson Cancer Center has dosed the first patient in a Phase 1 immunotherapy clinical trial investigating ipilimumab and evofosfamide for the treatment of patients with metastatic or locally advanced prostate cancer, metastatic pancreatic cancer, melanoma or human papillomavirus (HPV) negative squamous cell carcinoma of head and neck for which standard therapy does not offer the potential for increased survival.

“We believe that adding evofosfamide to certain immunotherapies has the potential to render some of the most therapeutically resistant cancers more sensitive to the immunotherapy, and we are excited to have dosed the first patient in this study,” said Tillman Pearce, MD, Chief Medical Officer at Threshold Pharmaceuticals. “Thanks to preclinical research conducted by Dr. Curran at MD Anderson Cancer Center, it is well-understood that certain tumors have hypoxic zones that resist infiltration by T cells, which are capable of attacking and killing tumor cells, and that combination therapy with evofosfamide and anti-CTLA-4/anti-PD-1 treatment opens up the hypoxic zones to T cell infiltration.”

Evofosfamide (also known as TH-302) is Threshold’s proprietary, hypoxia-activated prodrug of a bis-alkylating agent that is preferentially activated under severe hypoxic tumor conditions, a feature of many solid tumors. In preclinical research conducted by Michael Curran, PhD, Assistant Professor at the University of Texas MD Anderson Cancer Center, evofosfamide has sensitized highly resistant solid tumor models to treatment with certain immune checkpoint inhibitors through evofosfamide-driven disruption of hypoxic zones. Specifically, hypoxia in the tumor microenvironment forms a barrier to T cell infiltration and fosters immunotherapy resistance in prostate cancer and other solid tumors.

The Phase 1 clinical trial is a single-arm, open label study that will enroll up to 69 patients with metastatic or locally advanced prostate cancer, metastatic pancreatic cancer, melanoma or HPV-negative squamous cell carcinoma of head and neck. Eligible patients will receive evofosfamide on days 1 and 8 of the first two cycles and ipilimumab on day 8 of a 28-day cycle. Immune-related Response Evaluation Criteria In Solid Tumors (irRECIST) response rate is the primary endpoint. Secondary endpoints include duration of response, progression-free survival, overall survival, safety, tolerability and pharmacokinetics. The study is open at MD Anderson Cancer Center in Houston, TX. More details can be found here.

Evofosfamide (previously known as TH-302) is an investigational hypoxia-activated prodrug of a bis-alkylating agent that is preferentially activated under severe hypoxic tumor conditions, a feature of many solid tumors. Areas of low oxygen levels (hypoxia) in solid tumors are due to insufficient blood vessel supply. Similarly, the bone marrow of patients with hematological malignancies has also been shown, in some cases, to be severely hypoxic. Discussions remain ongoing with the Japanese PMDA regulatory agency on what additional clinical trials may be required to support submission of evofosfamide for the treatment of pancreatic cancer patients in Japan.

Threshold is a clinical-stage biopharmaceutical company focused on the development of drugs and diagnostic agents targeting the tumor microenvironment of solid tumors and hematologic malignancies. This approach offers broad potential to treat a variety of cancers. By selectively targeting tumor cells, we are building a pipeline of drugs that hold promise to be more effective and less toxic to healthy tissues than conventional anticancer drugs.