Three years after securing a series A round backed by OrbiMed in 2023, Sidewinder Therapeutics has raised additional capital through a $137 million series B financing led by a group of new investors. The San Diego-based biotech plans to use the funds to support its goal of entering the clinic in 2027.
The company is advancing a bispecific antibody-drug conjugate (ADC) platform aimed at treating solid tumors, as outlined in an April 8 announcement.
The latest round was co-led by Frazier Life Sciences and Novartis Venture Fund, with participation from Goldman Sachs Alternatives’ life sciences arm, Astellas Venture Management, DCVC Bio, S, Longwood Fund, Alexandria Venture Investments and amsara BioCapital. With this raise, Sidewinder Therapeutics has now secured a total of $162 million in funding.
Eric Murphy, co-founder and CEO of Sidewinder, said in a release that the company welcomes backing from a strong group of investors who share its commitment to advancing next-generation bispecific ADCs for cancers that are challenging to treat. He added that the ADC space is reaching a pivotal moment due to recent technological advances enabling these newer approaches and said Sidewinder aims to be at the forefront of this shift while progressing promising therapies for patients.
Sidewinder’s ADC strategy is designed to bind two receptors commonly found on tumor cells – one involved in driving cancer growth and another responsible for transporting signals into the cell. By targeting both, the company aims to selectively attack cancer cells while ensuring efficient delivery of therapeutic payloads deep within tumors.
Its pipeline spans multiple cancer types, including lung, head and neck, gastrointestinal and colorectal cancers. The company plans to submit an investigational new drug application for its lead candidate, SWT012, by the end of 2026. This candidate has already been evaluated in animal models of bladder cancer.
Additional pipeline assets include SWT019 and SWT020, which have undergone preclinical testing in lung and colorectal cancer models, respectively. Sidewinder Therapeutics expects to file an IND for SWT019 and finalize the formulation for SWT020 in the first half of next year.
Daniel Estes, general partner at Frazier Life Sciences, said in a release that Sidewinder’s bispecific ADC pipeline could help overcome important limitations affecting the safety and effectiveness of this therapeutic class. He added that the firm believes Sidewinder Therapeutics is well positioned to drive meaningful progress in the ADC field and reshape how cancer is treated for patients.
Sidewinder Therapeutics kicked off the year by entering a partnership with Synaffix, a Lonza company, securing access to its ADC technology in exchange for upfront payments and potential milestone-based compensation.
Meanwhile, OrbiMed has remained active despite broader headwinds in the biotech sector. After closing a $1.86 billion fund in August, the firm has quickly deployed capital across several investments, including Sparrow Pharmaceuticals’ $95 million series B, Electra Therapeutics’ $183 million series C and AirNexis Therapeutics’ $200 million series A. More recently, Pinnacle Medicines, a company founded by the venture firm, raised $89 million at the end of March.
Details of the Series B Financing
The $137 million Series B round includes participation from OrbiMed, alongside major investors such as Frazier Life Sciences and Novartis Venture Fund. The financing was oversubscribed, reflecting strong investor confidence in Sidewinder’s technology and pipeline.
For OrbiMed, this marks a continued investment in Sidewinder, following its role as an early backer in the company’s Series A funding.
What Sidewinder Is Developing
Sidewinder Therapeutics is focused on developing next-generation bispecific antibody-drug conjugates (ADCs) for cancer treatment. These therapies are designed to target tumor-specific receptor combinations, improving precision and minimizing damage to healthy cells.
With backing from OrbiMed, Sidewinder aims to advance its lead programs into clinical development, targeting difficult-to-treat cancers such as lung, colorectal, and head and neck cancers.
The involvement of OrbiMed in this financing signals strong momentum in the ADC market. Investors are increasingly focusing on technologies that enhance drug specificity and efficacy.
For OrbiMed, this deal reinforces its reputation as a key player in funding transformative biotech innovations.
What’s Next for OrbiMed and Sidewinder
Following the financing, OrbiMed is expected to continue supporting Sidewinder as it progresses toward clinical trials. The company plans to advance its lead candidate and expand its pipeline using the newly raised capital.
For OrbiMed, this investment could yield long-term returns if Sidewinder’s technology proves successful in clinical settings.
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