Sidewinder Therapeutics announced on Apr. 9 that it has raised $137 million in a series B funding round to support the development of bispecific antibody-drug conjugates for solid tumors with limited treatment options.
The funding aims to help Sidewinder progress its lead program, which the company plans to bring into clinical trials next year. According to the announcement, the candidate—referred to as SWT012—has undergone animal testing for bladder cancer and is expected to have an investigational new drug (IND) submission by year-end.
In addition to SWT012, Sidewinder is developing other bispecific antibodies, including SWT019 and SWT020. Preclinical studies have tested these candidates for lung and colorectal cancers, respectively. The company intends to file an IND for SWT019 in the first half of 2027 while finalizing a formula for SWT020.
Sidewinder’s technology platform creates bispecific ADCs that target specific protein co-complexes found on certain cancers. By focusing on two targets instead of one, this approach seeks better delivery of therapeutic payloads directly to malignant cells while reducing effects on healthy cells. The company is pursuing indications such as squamous lung and head and neck cancers that affect large patient populations with few treatment options.
The series B fundraising was led by Novartis Venture Fund and Frazier Life Sciences, with participation from OrbiMed—its sole series A investor last year—as well as Astellas Venture Management, Samsara BioCapital, and Life Sciences at Goldman Sachs Alternatives. With this latest round, Sidewinder has raised a total of $162 million since its founding.
This fundraising places Sidewinder among several biotechs recently securing significant investments despite industry challenges.
