Endocyte said today it has licensed ABX’s radioligand therapeutic (RLT) candidate PSMA-617 in a deal that could generate up to $172 million-plus for the German nuclear medicine company, adding that it will refocus the company’s development efforts around the prostate cancer treatment.

During the first half of 2018, Endocyte plans to launch a Phase III trial for the RLT that it calls 177Lu-PSMA-617, which targets the prostate-specific membrane antigen (PSMA), present in approximately 80% of patients with metastatic castration-resistant prostate cancer (mCRPC). 177Lu-PSMA-617 is designed to deliver the short-range beta-emitting radioactive isotope lutetium (177Lu) selectively to tumor cells while by-passing non-PSMA-expressing healthy cells.

In post-chemotherapy compassionate use, 177Lu-PSMA-617 has shown encouraging efficacy and safety results, Endocyte said—citing results from approximately 20 peer-reviewed studies that have shown a PSA response in 40% to 60% of patients, and a RECIST response rate in soft tissue disease of between 40% and 50%.

“This transaction is transformational to Endocyte, accelerating our path to commercialization. 177Lu-PSMA-617 has the potential to be the first-in-class RLT to address both bone and soft tissue disease, and it is profoundly important to the many patients suffering from mCRPC,” Endocyte president and CEO Mike Sherman said in a statement. “Our experience with PSMA targeting and companion imaging development, in addition to our relationships with distinguished prostate cancer investigators from around the world, uniquely position Endocyte to lead this therapy to registration.”

So encouraged is Endocyte by 177Lu-PSMA-617, Sherman added, that the company will explore out-licensing opportunities for all of its other development programs—except for its chimeric antigen receptor T-cell (CAR T-cell) program, for which he said Endocyte will work to generate proof-of-concept data.

“177Lu-PSMA-617 has demonstrated the most compelling activity of any drug currently in development for these post-chemotherapy patients,” added Endocyte’s CMO, Alison A. Armour, M.B., Ch.B., M.D., MRCP, FRCR.

Change of Direction

Endocyte agreed to pay ABX $12 million upfront, up to $160 million in payments tied to achieving regulatory and commercial milestones, and tiered royalties beginning in the mid-teens. In addition, Endocyte issued 2 million shares of Endocyte common stock to ABX and issued a warrant for the purchase of up to 4 million additional shares of Endocyte common stock

Endocyte’s repivot marks its second change of direction this year.

The first came in June, when the company eliminated 40% of its workforce, or approximately 30 jobs, and overhauled its clinical development effort by refocusing on its CAR T-cell and dual-targeted DNA crosslinker drug EC2629 programs.

Endocyte also ended clinical development of its folate receptor-targeted tubulysin solid tumor cancer candidate EC1456 and its prostate-specific membrane antigen (PSMA)-targeted tubulysin prostate cancer therapy EC1169 in taxane-naïve patients, while continuing EC1169 development in taxane-exposed patients.

Endocyte elaborated in August, saying it expected to complete enrollment of taxane-exposed prostate cancer patients in a PSMA-tubulysin expansion trial of EC1169 this fall. The company added that it was continuing enrollment of a “small number” of patients in its EC1456 ovarian cancer surgical study “to inform other small-molecule drug conjugate programs in development,” though it halted a Phase Ib trial because the assessment of trial data did not yield the level of clinical activity necessary to support continued advancement of EC1456.

PSMA-617 was developed at DKFZ (German Cancer Research Center) and University Hospital Heidelberg and was exclusively licensed to ABX for early clinical development.