FDA Grants Orphan Drug Designation to PT217 for Small Cell Lung Cancer


Orphan drug designation has been granted by the FDA to PT217 for patients with small cell lung cancer.

The FDA has granted an orphan drug designation to the first-in-class bispecific antibody, PT217, as a potential treatment option for patients with small cell lung cancer (SCLC), according to Phanes Therapeutics.1

This orphan drug designation follows 2 investigational new drug application clearances, including PT199, an anti-CD73 monoclonal antibody, and PT886, an anti-Claudin 18.2/anti-CD47 bispecific antibody.

“PT217 has the potential to be a transformative treatment option for SCLC patients whose initial response to chemotherapy is short-lived and inevitably becomes resistant to chemotherapeutic agents,” stated Ming Wang, PhD, MBA, chief executive officer of Phanes Therapeutics, in the press release. “We have built a strong pipeline in immuno-oncology by leveraging our proprietary technology platforms and expect to file an [investigational new drug application] for PT217 by the third quarter of this year.”

PT217 is designed to target delta-like ligand 3 (DLL3) and cluster of differentiation 47 (CD47) in patients with SCLC as well as other neuroendocrine cancers. DLL3 and CD47 are each clinically validated targets and are highly expressed in SCLC.

PT217 works to specifically target SCLC cells via 2 mechanisms. The first is that PT217 blocks its interaction with CD47-SIRPα and stimulates phagocytosis of tumor cells by macrophage, and the second is that PT217 is designed to mediate robust antibody-dependent cellular cytotoxicity for tumor cells by NK cells.

As a result, the tumor cells that are targeted by NK cells end up subsequently engulfed by macrophage. Additionally, with an elevated phagocytosis of the tumor cells by macrophages and dendritic cells, it is expected by investigators that there will also be an increase in the presentation of tumor neoantigens which would then lead to T-cell mediated killing of tumor cells, irrespective of DLL3 expression.

In a poster presented at the 2022 AACR Annual Meeting, investigators noted that PT217 displayed robust tumor suppression activity in a preclinical trial.2

As a result, investigators proposed the design of a phase 1 dose-escalation clinical study to investigate PT217 in patients with DLL3-positive SCLC, large cell neuroendocrine carcinoma, and neuroendocrine prostate cancer. The structure included a dose escalation–guided 3+3 design which would examine PT217 when given to approximately 14 evaluable patients in weekly doses at 5 different dose levels.

The initiation of the phase 1 trial to target SCLC is planned for the later half of 2022.

  1. Phanes therapeutics' PT217 receives orphan drug designation for small cell lung cancer from the FDA. News release. Phanes Therapeutics. June 21, 2022. Accessed June 21, 2022. https://prn.to/3tR1l0Y
  2. Jia H, Fang D, Lobsinger M, et al. PT217, an anti-DLL3/anti-CD47 bispecific antibody, exhibits anti-tumor activity through novel mechanisms of action. Presented at: 2022 AACR Annual Meeting; April 8-13, 2022; New Orleans, LA. Abstract 2908
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