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Biliary Cancer Bispecific Antibody Spevatamig Granted FDA Fast Track Designation
This regulatory designation opens a channel for more frequent FDA communication on Phanes’ dual-targeting CLDN18.2/CD47 strategy, but its actual clinical value must still be demonstrated by the ongoing early-stage trial, which is currently recruiting.
Advanced biliary tract cancer has gained another experimental immunotherapy avenue. The U.S. Food and Drug Administration (FDA) has granted Fast Track designation to spevatamig, a bispecific antibody under development by Phanes Therapeutics, for advanced and metastatic biliary tract cancer. The designation may help the company communicate more frequently with the FDA regarding its development program, but it does not mean the drug has been approved, nor can it predict trial results.
Spevatamig, also known as PT886, is a native IgG-like bispecific antibody that recognizes both CLDN18.2 and CD47. The former may be expressed on the surface of some gastrointestinal tumor cells, while the latter is involved in signaling that allows tumors to evade immune phagocytosis. Through dual binding, Phanes aims to direct immune activity more selectively toward tumors. However, whether this design can translate into acceptable efficacy and safety cannot currently be determined because pivotal trial data in biliary tract cancer are not yet available.
The drug is being evaluated in the Phase I/II open-label TWINPEAK trial. ClinicalTrials.gov data show that the study covers unresectable or metastatic biliary tract cancer, gastric cancer, gastroesophageal junction cancer, and pancreatic ductal adenocarcinoma, testing spevatamig as monotherapy and in combination with chemotherapy or immune checkpoint inhibitors. The trial is expected to enroll 258 participants and is still recruiting. Its primary assessments include safety, tolerability, the recommended expansion dose, and preliminary antitumor activity.
In its biliary tract cancer development program, Phanes initiated dose expansion of spevatamig in combination with chemotherapy in April 2026, after the two preceding dose levels passed the dose-limiting toxicity observation period. As of March of the same year, the company said that more than 160 patients worldwide had received spevatamig as monotherapy or in combination regimens. This figure reflects overall exposure experience but cannot directly answer questions about response rate, duration of response, or survival benefit in patients with biliary tract cancer.
The development program is also expanding into frontline treatment. Phanes and Merck established a collaboration in 2023 and expanded the agreement in July 2026 to prepare for an evaluation of spevatamig, pembrolizumab, and chemotherapy as first-line treatment for biliary tract cancer. The trial registration lists Merck as a collaborator and also includes the relevant drug combinations. To demonstrate that the three-drug regimen is superior to existing treatment, it will still be necessary to determine whether the additional immune activity provides sufficient clinical benefit to offset toxicity and treatment burden.
The FDA Fast Track program is intended to facilitate the development of drugs for serious conditions that may address unmet medical needs and may provide regulatory advantages such as rolling submissions, although such arrangements remain subject to subsequent conditions. For spevatamig, the next more informative milestone is not the designation itself, but whether the biliary tract cancer expansion cohort can produce interpretable data on efficacy, safety, and patient selection.