Three years after its OrbiMed-backed series A in 2023, Sidewinder Therapeutics is adding to its nest egg courtesy of a clutch of new investors. The San Diego startup has sunk its teeth into a $137 million series B that will power preparations for a 2027 clinical debut.
Sidewinder’s signature approach is a bispecific antibody-drug conjugate technique, which the company is developing for solid tumors, according to an April 8 release.
Joining OrbiMed in the fundraising are Frazier Life Sciences and Novartis Venture Fund, who led the round, along with Life Sciences at Goldman Sachs Alternatives, DCVC Bio, Samsara BioCapital, Longwood Fund, Astellas Venture Management and Alexandria Venture Investments.
The series B brings Sidewinder’s total haul to $162 million, according to the release.
“We are pleased to receive the support of this exceptional group of investors and their shared enthusiasm in advancing Sidewinder’s mission to develop next-generation bispecific ADCs for difficult-to-treat cancers,” Eric Murphy, Ph.D., Sidewinder’s co-founder and CEO, said in the release. “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 and advance promising therapies for patients with cancer.”
Sidewinder’s ADCs are designed to target pairs of receptors that are common on some tumor cells. One of these receptors drives the tumor’s growth, while another is used to shuttle external signals into the tumor’s interior. By binding both, Sidewinder said, the goal is to specifically target only cancer cells and ensure that drug payloads are delivered deep inside the tumor.
The biotech’s programs are targeting lung cancer, head and neck cancers, gastrointestinal cancers and colorectal cancer, according to the release. The biotech plans to file an investigational new drug application for its lead asset, SWT012, by the end of 2026, according to a corporate presentation shared with Fierce Biotech.
SWT012 has been tested in animal models of bladder cancer, the presentation said, while other bispecifics, SWT019 and SWT020, have been preclinically tested in lung cancer and colorectal cancer, respectively. An IND application for SWT019 and the selection of a final formulation of SWT020 are set to follow in the first half of 2027.
“Sidewinder’s novel bispecific ADC pipeline has the potential to address key hurdles limiting safety and efficacy for this class of therapeutics,” Daniel Estes, Ph.D., general partner at Frazier Life Sciences, said in the release. "We believe that Sidewinder Therapeutics will significantly advance the ADC space and is well-positioned to transform the treatment paradigm for cancer patients.”
Sidewinder started the year with a new partnership with Lonza company Synaffix, with Sidewinder offering upfront and milestone payments for access to Synaffix’s ADC technology.
Despite last year’s challenges for the biotech industry, OrbiMed closed a $1.86 billion fund in August and has not tarried in putting the cash to use. The outfit has pitched in to Sparrow Pharmaceuticals’ $95 million series B, Electra Therapeutics’ $183 million series C and AirNexis Therapeutics’ $200 million series A. Most recently, Pinnacle Medicines, which was founded by the VC firm, brought in $89 million at the end of March.