Pieris Pharmaceuticals has announced the dosing of the first subject in Phase II clinical trial of the drug candidate, cinrebafusp alfa (PRS-343), to treat human epidermal growth factor receptor 2 (HER2)-expressing gastric cancer. 

A 4-1BB/HER2 fusion protein, cinrebafusp alfa includes 4-1BB-targeting Anticalin proteins, as well as an antibody that acts on HER2.

The drug is currently being analysed in a Phase II trial to treat HER2-expressing solid tumours. 

The multicentre, two-arm, open-label trial will assess the safety, efficacy and tolerability of cinrebafusp alfa plus ramucirumab and paclitaxel in individuals with HER2-high gastric cancer, and along with tucatinib in HER2-low gastric cancer patients.

Trial subjects will be given an 18mg/kg loading dose in weeks one and three and subsequently 8mg/kg maintenance doses once every two weeks (Q2W). 

In the HER2-low group, Pieris anticipates an ORR of a minimum of 40% and significant durability, with results expected later this year. 

The company aims for an ORR of a minimum of 50% with considerable durability for the HER2-high arm, with data anticipated next year. 

Pieris Pharmaceuticals chief medical officer Tim Demuth said: “The dosing of the first patient in this next phase of development of cinrebafusp alfa marks an important milestone for patients afflicted by gastric cancer without adequate treatment options, and we look forward to further evaluating the potential of this drug. 

“We believe cinrebafusp alfa can provide differentiated treatment options for patients with gastric cancer via 4-1BB-mediated T-cell engagement, both in terms of efficacy and safety.”

In Phase I trials, cinrebafusp alfa demonstrated to have an acceptable safety profile at all the dose levels tested without any dose-limiting toxicities. 

Furthermore, based on clinical benefit and pharmacodynamic correlates, the drug was found to have a dose-response and a 4-1BB-driven mechanism of action. 

In June 2021, Pieris received a grant for the development of PRS-220 for treating post-acute sequelae of SARS-CoV-2 infection (PASC) pulmonary fibrosis (PASC-PF) or long Covid.