Sidewinder Therapeutics has raised $137 million in a Series B financing round that will be used to advance newer types of antibody-drug conjugates, or ADCs, into clinical testing.
Sidewinder is part of a wave of companies aiming to improve upon ADC technology. These drugs, which chemically link a toxic payload to a targeting molecule, have come of age in recent years as a more precise way to kill cancer. But their reach still remains limited, spurring investment in developers working on new methods to take the field a step further.
In Sidewinder’s case, the company is pursuing bispecific ADCs able to recognize and bind to protein combinations that are highly expressed on cancer cells. These complexes consist of one protein receptor that helps drive cancer, and another that pulls substances into cells. Sidewinder believes focusing on these combinations could lead to a more targeted and effective attack on tumors.
“The ADC field is at an inflection point driven by technological breakthroughs enabling next-generation bispecific ADCs, and Sidewinder is eager to lead this wave of innovation,” said Eric Murphy, Sidewinder’s CEO and co-founder, in a statement.
Sidewinder said it will focus on cancer indications — like colorectal tumors and squamous cell carcinomas — that affect large populations but have limited treatment options. The company expects to push its lead program into clinical development in 2027, but didn’t specify the drug’s targets.
Sidewinder was founded in 2023 with Series A backing from OrbiMed. Including the latest funding, the startup has now raised a total of $162 million. It recently partnered with Lonza’s Synaffix subsidiary to gain access to an ADC technology that’s been licensed to several other firms.
The latest financing was co-led by Frazier Life Sciences and the venture arm of Novartis, and involved OrbiMed, Astellas Venture Management and multiple other firms.
OrbiMed is consistently one of the biotech sector’s most active investors, having participated in around 90 rounds for drug startups since the start of 2022, according to BioPharma Dive data. Last August, the firm closed a $1.86 billion fund focused on credit- and royalty-based financing.