Benzinga | Dec 2, 2021 08:06AM EST

Onconova Therapeutics Announces The Presentation Of Preliminary Clinical Data Providing Evidence Of Rigosertib's Activity In RDEB-associated Squamous Cell Carcinoma

Onconova Therapeutics, Inc. (NASDAQ:ONTX), a clinical-stage biopharmaceutical company focused on discovering and developing novel products for patients with cancer, today announced that early preliminary data from an investigator-initiated Phase 2 open label trial of rigosertib monotherapy in advanced squamous cell carcinoma complicating recessive dystrophic epidermolysis bullosa (RDEB-associated SCC) were presented at the Austrian Society of Dermatology and Venerology Annual Conference 2021, which took place from November 25 -- 27, 2021.

RDEB is an ultra-rare condition caused by a lack of type VII collagen protein expression. Type VII collagen protein is responsible for anchoring the skin's inner layer to its outer layer, and its absence leads to extreme skin fragility and chronic wound formation in RDEB patients. Over time, many of these patients develop squamous cell carcinomas (SCCs) that typically arise in areas of chronic skin wounding and inflammation. Preclinical investigations demonstrated overexpression of polo like kinase 1 (PLK1) in RDEB-associated SCC tumor cells. These tumors show a highly aggressive, early metastasizing course, making them the primary cause of death for these patients, with a cumulative risk of death of 70% and 78.7% by age 45 and 55, respectively1,2. These neoplasms show limited response rates of mostly short duration to conventional chemo- and radiotherapy as well as targeted therapy with epidermal growth factor and tyrosine kinase inhibitors1,3.

Data from the recent presentation are from a 24-year-old RDEB patient with a history of multiple, unresectable SCCs that were unresponsive to prior treatments including cemiplimab. Results showed that intravenously administered rigosertib had an acceptable safety profile and that the patient experienced sustained clinical and histological remission of all target lesions without signs of metastatic disease following 13 treatment cycles. The patient remains on study and the trial remains ongoing. The enrollment of additional patients is anticipated at sites in Salzburg, Austria; London, UK; and Philadelphia, Pennsylvania.

"Though the trial's currently available data are from only a single patient, they represent an exciting and powerful finding that warrants further study," said Andrew South Ph.D., Associate Professor, Department of Dermatology & Cutaneous Biology, Thomas Jefferson University. "RDEB-associated SCC is an indication with an extremely high unmet medical need, as it is invariably fatal with treatment options that have so far yielded disappointing results. The data generated in preclinical models suggesting rigosertib's robust activity against PLK1 have now been confirmed in the clinic and suggest that rigosertib may play a role in other more common cancers driven by PLK1."

The physicians caring for the patient, Dr. Bauer, Principal Investigator, and Dr. Laimer, Sponsor Medical Expert of the trial, added in a joint statement, "To see a complete response in a patient that has failed multiple prior therapies is highly encouraging and, together with preclinical data, suggests that rigosertib's ability to inhibit PLK1 may position it as a novel treatment option that can significantly improve upon the current standard-of-care. We look forward to the further evaluation of this hypothesis through the continued advancement of the trial."

A copy of the poster, titled "Rigosertib for locally advanced/metastatic EB-associated SCC," is available on the "Scientific Presentations" section of the Onconova website.