Chimerix said today it will develop Cantex Pharmaceuticals’ Phase III-bound CX-01 as a first-line treatment for Acute Myeloid Leukemia (AML) and possibly other blood cancers, through an exclusive worldwide licensing agreement that could generate more than $617.5 million for Chimerix.

CX-01 is a new chemical entity derived from unfractionated heparin with very low anticoagulant activity. CX-01 is designed to target key protein pathways deemed important for AML blast cell migration to the bone marrow and retention of these cells in the marrow where they are protected from chemotherapy. CX-01 is also designed to bind with proteins involved in chemotherapy resistance and the delay in platelet recovery following chemotherapy.

The combined mechanisms of action are understood, according to Chimerix, to sensitize AML blasts to chemotherapy and improve clinical responses—supporting the potential for developing the drug in myelodysplastic syndrome, multiple myeloma, and lymphomas. CX-01 has received the FDA’s Fast Track and Orphan Drug designations for the treatment of AML.

“CX-01’s mechanism of action, targeting multiple proteins involved in protecting and supporting the growth of cancer cells, provides opportunities for potential development across a range of hematologic malignancies,” Chimerix CEO Mike Sherman said in a statement. “We are excited to advance this promising product candidate in AML as it has shown compelling activity across multiple endpoints in first-line patients as opposed to later lines of therapy where most of the recent advances in this disease area have occurred.”

Chimerix said it plans to launch a Phase III trial of CX-01 in mid-2020.

89% complete response rate

The licensing agreement comes some two months after Cantex presented Abstract 7001 showing positive mid-stage data for CX-01 at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting, held May 31–June 4 in Chicago.

The data came from a Cantex Phase II trial (NCT02873338) that showed patients dosed with 0.25 mg/kg/hr of CX-01 plus chemotherapy fared better than patients in the control arm of chemotherapy alone in complete response or CR rate (89% vs. 58%), and median event-free survival or EFS (23.4 months vs. 9.0 months). Median overall survival had not yet been reached on the CX-01 arm vs. 11.2 months for chemo.

In the trial, 75 patients over age 60 with newly diagnosed AML were randomized 1:1:1 to one of two doses of CX-01 (0.125 mg/kg/hr or 0.250 mg/kg/hr) plus standard 7+3 chemotherapy (7 days of cytarabine, 3 days of anthracycline) or to the control arm of standard 7+3 chemotherapy alone.

“The encouraging CR rate and EFS in elderly fit patients with newly diagnosed AML suggests that CX-01 may potentiate the efficacy of standard AML induction therapy,” the researchers concluded.

One of those researchers, Paul Shami, MD, of Huntsman Cancer Institute and the University of Utah, stated today: “If our results are confirmed, combining CX-01 with chemotherapy has the potential to have a significant impact on the outcomes of patients suffering from one of the most challenging hematologic malignancies.”

CX-01 is one of two candidates in Chimerix’s pipeline. The other is Brincidofovir (BCV, CMX001), an anti-viral drug candidate in development as a medical countermeasure for smallpox. In 2011, Chimerix received an $81 million grant from the U.S. Biomedical Advanced Research and Development Authority (BARDA) to explore development of brincidofovir to treat potential smallpox outbreaks in the event of a bioterror attack or accidental release.

“Repositioning the company”

In December 2015, brincidofovir failed a Phase III trial assessing the drug’s ability to prevent cytomegalovirus (CMV) in hematopoietic cell transplantation (HCT). As a result, the company eliminated about 20% of its workforce.

“We are pleased to have made such rapid progress in repositioning the company and transforming our pipeline with this important cancer therapy,” Sherman said. “With more than 21,000 new cases of AML diagnosed annually in the U.S. alone and a five-year survival rate of less than 30%, the patient need is clear.”

The American Cancer Society estimates about 21,450 new cases of AML in the U.S. this year, most of them in adults, with about 10,920 deaths from AML occurring.

Chimerix obtained exclusive worldwide rights to develop and commercialize CX-01 in return for agreeing to pay Cantex $30 million upfront, up to $587.5 million in payments tied to achieving regulatory and commercial milestones, as well as tiered royalties starting at 10%.

Chimerix also agreed to issue 10 million shares of Chimerix common stock to Cantex. Shares of Chimerix closed yesterday at $3.52, bringing the value of those shares to $35.2 million. That value rose nearly 3% this morning, as investors sent the price of Chimerix shares climbing to $3.62 in early trading as of 10 a.m.

“We are very pleased to be partnering with Chimerix and their world-class scientists,” added Cantex CEO Stephen Marcus, MD. “We believe that Chimerix management’s track record in developing novel cancer therapeutics makes Chimerix the perfect partner to aggressively advance the development of CX-01 for the treatment of AML and other hematologic malignancies.”

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