BOSTON, MA, USA I August 17, 2023 I Pieris Pharmaceuticals, Inc. (NASDAQ:PIRS), a clinical-stage biotechnology company focused on novel biotherapeutics through its proprietary Anticalin® technology platform for respiratory diseases and cancer, today announced that the Company has achieved an undisclosed milestone payment from Boston Pharmaceuticals. The milestone is based on dosing the first patient in a Boston Pharmaceutical-sponsored phase 1/2 study of BOS-342 (formerly PRS-342), a 4-1BB/GPC3 immuno-oncology antibody-Anticalin fusion (Mabcalin™) bispecific protein, which was discovered by Pieris and licensed to Boston Pharmaceuticals and designed to provide a potent costimulatory bridge to exert tumor killing activity through the recruitment of T-cells.

The open-label phase 1/2 study is designed to evaluate the safety, tolerability, pharmacokinetics, and efficacy of BOS-342. The Phase 1 dose escalation portion of the study is expected to enroll adults with hepatocellular carcinoma (HCC) that progressed on at least one prior treatment and establish a recommended Phase 2 dose. If pursued, the Phase 2 portion of the study will evaluate efficacy, as measured by overall response rate.

The study is funded and conducted by Boston Pharmaceuticals, who exclusively licensed worldwide rights to BOS-342 in April 2021. In addition to the milestone announced today, Pieris could potentially be entitled to receive up to approximately $350 million in development, regulatory and sales-based milestone payments, and tiered royalties on sales of BOS-342.

“We are delighted with Boston Pharmaceuticals’ commitment to BOS-342, now having initiated clinical development of yet another promising 4-1BB bispecific Mabcalin program originating from our platform and representing the fourth 4-1BB-targeted therapy that has entered clinical stage development,” said Stephen S. Yoder, President and CEO of Pieris. “4-1BB is a highly promising target for cancer immunotherapy, and our multiple partnerships in this area validate the potential that 4-1BB-based bispecific therapies may play in advancing cancer therapeutics.”

“Dosing of the first patient with BOS-342 represents an important milestone for the BOS-342 program and, more importantly, for patients with HCC, many of whom often do not achieve durable benefit from current available treatment regimens,” said Sophie Kornowski, CEO of Boston Pharmaceuticals. “Preclinical data strongly support our belief that BOS-342 has the potential to address a significant unmet need as a treatment for patients with GPC3+ HCC.”

About Pieris Pharmaceuticals:

Pieris is a clinical-stage biotechnology company that combines leading protein engineering capabilities and deep understanding into molecular drivers of disease to develop medicines that drive local biology to produce superior clinical outcomes for patients. Our pipeline has historically focused on inhalable Anticalin proteins to treat respiratory diseases and locally-activated bispecifics for immuno-oncology. Proprietary to Pieris, Anticalin proteins are a novel class of therapeutics validated in the clinic and by strong partnerships with leading pharmaceutical companies. For more information, visit

SOURCE: Pieris Pharmaceuticals