Immunomedics, a clinical-stage biopharmaceutical company developing antibody-based products for the targeted treatment of cancer, autoimmune disorders and other serious diseases, has received a new patent (U.S. Patent 9,375,489) covering the composition and uses of sacituzumab govitecan, also known as IMMU-132, the company’s lead cancer therapeutic. The patent, entitled “Antibody-SN-38 Immunoconjugates with a CL2A Linker” is the 28th issued U.S. patent for this novel drug.
Sacituzumab govitecan is an antibody-drug conjugate or ADC comprising a humanized antibody to the cancer marker, Trop-2, conjugated with SN-38, the active metabolite of the well-known anticancer drug, irinotecan. This novel cancer therapeutic is in development for the treatment of patients with many diverse solid cancers.
The most advanced indication in development of sacituzumab govitecan in triple-negative breast cancer (TNBC), a hard to treat cancer which is estrogen receptor-negative, progesterone receptor-negative and HER2-negative, with Phase II studies also continuing in patients with metastatic non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC),  and in patients with metastatic urothelial cancers. 
An interim median progression-free survival (PFS) and overall survival (OS) were 3.9 months (95% confidence interval [CI]; 3.4, 6.9) and 10.5 months (95% CI; 5.8, 10.5), respectively. Significant tumor shrinkage and disease stabilization was observed in both adenocarcinoma and squamous cell carcinomas, the two major subtypes of NSCLC, and in patients who had failed previous anti- PD-1/PD-L1 therapy.
Metastatic urothelial cancer
Sacituzumab govitecan also produced meaningful clinical benefit in patients with relapsed or refractory metastatic urothelial cancer. Among the 19 patients enrolled into the open-label Phase 2 study, at the time of analysis the interim median PFS was 6.9 months, based on RECIST 1.1, and interim mean OS was 11.4 months, with 84% of patients still alive. 
This most recent patent expires in 2029, but other patents covering this product and technology have expiration dates to 2033. The diverse patents have claims for composition of matter, including the antibody and linker molecule, increased number of drugs per antibody, uses in various cancers, including different dose schedules, and other proprietary features of the ADC.
“This extensive patent coverage complements the 12-year biotechnology exclusivity in the U.S. for such products, we believe, and enhances this agent’s potential commercial value,” noted Cynthia L. Sullivan, Immunomedics President and Chief Executive Officer.
“We have also received claims in many of these patents in other countries, and continue to prosecute additional patent applications for our ADC platform technology worldwide,” Sullivan added.
Immunomedics also related its updated clinical development plan for sacituzumab govitecan in TNBC, based on a recent Breakthrough Therapy Designation (BTD) and a follow-on meeting with the U.S. Food and Drug Administration (FDA).
In the fall of this year, Immunomedics plans to complete enrolling additional patients with relapsed/refractory metastatic TNBC who have received at least two prior therapies, including taxane, for metastatic disease into the ongoing single-arm Phase II study. Results from this Phase II study are expected to support the clinical requirements for pursuing Accelerated Approval. All patients receive repeated cycles of sacituzumab govitecan at the dose of 10 mg/kg on days 1 and 8 of a twenty-one day cycle.
Treatment responses, including overall response rate and duration of response, are assessed with computed tomography (CT) in accordance with RECIST 1.1, and confirmed by an independent centralized and blinded group of radiology experts.
Immunomedics is working with the FDA on these plans for completing the ongoing Phase II trial and for submitting an Accelerated Approval registration application, based on interactions with the agency. Furthermore, initial discussion has also occurred with the European Medicine Agency (EMA), which has provided Immunomedics with advice on its planned Phase III trial.
“This enrollment timeline will allow us to have at least six months of patient follow-up to obtain a confirmed response rate and a mature duration of response, which will be part of an Accelerated Approval application estimated to be submitted to the regulatory agency by the middle of calendar year 2017,” noted William A. Wegener, M.D., Ph.D., Chief Medical Officer of Immunomedics.
“It will also allow us to have our Phase III trial, which we have reached agreement with FDA on a Special Protocol Assessment (SPA), well underway, as required by the FDA for Accelerated Approval. Our goal is to make IMMU-132 available to metastatic TNBC patients as quickly as possible, given what we believe is the first time the FDA has granted a BTD in this indication,” he further remarked.
“Preparation for the commercial-scale manufacturing of the ADC using three outside contract manufacturing organizations (CMOs) is proceeding according to plan and Immunomedics hopes to begin the Phase III study, with drug supplied by our CMOs, in December 2016,” Sullivan said.
“To fund the Phase III confirmatory study and further clinical development of this important and valuable asset in other solid cancers, we continue to work with our outside advisory group, which we retained the beginning of this year, to assist us in bringing a licensing arrangement with a global corporate partner to completion,” Sullivan concluded.