Endocyte intends to move quickly into Phase 3 development of 1 Lu-PSMA-617, a radioligand therapeutic (RLT) that targets the prostate-specific membrane antigen (PSMA), present in approximately 80% of patients with metastatic castration-resistant prostate cancer (mCRPC).
Lu-PSMA-617 delivers the short-range beta-emitting radioactive isotope lutetium (177Lu) selectively to tumor cells while by-passing non-PSMA-expressing healthy cells with encouraging efficacy and safety results.
As highlighted in roughly 20 peer reviewed publications of studies in the post-chemotherapy compassionate use setting, 177 Lu-PSMA-617 has consistently demonstrated a PSA response (defined as greater than 50% decline from baseline) 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," said Mike Sherman, president and CEO of Endocyte.
"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. We intend to seek regulatory approval to initiate a Phase 3 registration trial of 177Lu-PSMA-617 in early 2018. By focusing the company's resources on the execution of this program, we project trial completion as early as 2020."
Mr. Sherman continued, "Endocyte remains strongly committed to careful expense management and maintaining a strong balance sheet. With the exception of a very targeted effort to generate proof-of-concept data for our CAR T-cell program, we will focus our resources on the development of 177Lu-PSMA-617. We will explore out-licensing opportunities for all other development programs."
"Despite advances in the last decade that slow the progression of prostate cancer, once metastasized it is nearly always lethal, leading to 300,000 worldwide deaths annually. 177Lu-PSMA-617 has demonstrated the most compelling activity of any drug currently in development for these post-chemotherapy patients," said Alison Armour, chief medical officer.
PSMA-617 was developed at DKFZ (German Cancer Research Center) and University Hospital Heidelberg and exclusively licensed to ABX GmbH in Germany for early clinical development. As a result of the enthusiasm of physician investigators and patients, the investigational therapy has been evaluated in hundreds of patients through both compassionate use studies and prospective trials.
"The data generated thus far have created significant enthusiasm for 177Lu-PSMA-617. PSMA is a promising target in prostate cancer and radioligand therapy may be the best application for this target," said Michael Morris, MD, associate professor, Genitourinary Oncology, Memorial Sloan Kettering Cancer Center.
"Particularly where disease has become resistant to current therapies, there is a tremendous need for new approaches and I look forward to working with Endocyte to investigate this innovative, first-in-class therapy for prostate cancer patients."
Clinical Data Presented at European Society for Medical Oncology (ESMO)
Dr. Michael Hofman of the Peter MacCallum Cancer Center in Melbourne, Australia presented the results of an open-label, single-arm, non-randomized pilot study of 177 Lu-PSMA-617 in September 2017, at the European Society for Medical Oncology (ESMO) Congress.
Thirty mCRPC patients were treated with up to four cycles of 4-8 GBq. Primary endpoints included safety and efficacy as defined by PSA response, quality of life, and imaging response.
The results showed a remarkable 57% PSA response rate ( > 50% reduction) and 71% interim response rate in soft tissue lesions (as measured by RECIST criteria) in patients who had previously failed such conventional therapies as docetaxel, cabazitaxel, enzalutamide and abiraterone.
Median overall survival was 12.7 months. The drug was well-tolerated, with a low rate of adverse effects and no renal toxicity. Significantly improved quality of life scores and reduction in pain scores were recorded in 37% and 43% of patients, respectively. This trial has subsequently been expanded to 50 subjects from the original 30, with updated results expected to be presented in 2018.
Transaction Terms
Under the terms of the agreement, Endocyte has exclusive worldwide rights to develop and commercialize PSMA-617. Endocyte has made an upfront payment of $12 million to ABX. 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.
ABX is eligible for regulatory and commercial milestones of up to $160 million, and tiered royalties beginning in the mid-teens.