Asher Bio Secures $55 Million in Series C to Propel CD8-Targeted Immunotherapy into Advanced Trials

Asher Bio, a biotechnology innovator specializing in precision-engineered immunotherapies, has successfully closed its Series C funding round, bringing in $55 million to accelerate clinical development of its promising pipeline. The funding round, anchored by RA Capital Management, marks a significant milestone for the company and reflects strong investor confidence in its differentiated approach to cancer treatment.

Investor Syndicate Expands with Industry Giants

The funding coalition includes two major pharmaceutical companies—AstraZeneca and Bristol Myers Squibb—joining existing backers such as Janus Henderson Investors, Third Rock Ventures, Wellington Management, and Boxer Capital. The participation of these established pharma players signals recognition of Asher Bio’s innovative immunotherapy platform and validates the company’s clinical progress to date.

According to Craig Gibbs, Ph.D., Chief Executive Officer of Asher Bio, the company is now positioned to deliver a new generation of highly selective, cell-type-specific immunotherapies. “Our approach is designed to activate only the desired immune cell populations, thereby maximizing therapeutic benefit while minimizing unwanted side effects,” Gibbs explained. “The robust investor demand for this round demonstrates confidence in both our early clinical evidence and our differentiated technical strategy.”

AB248: A Breakthrough in Targeted IL-2 Therapy

At the heart of Asher Bio’s strategy is AB248, a novel immunotherapy that represents a significant departure from conventional IL-2 approaches. The molecule is engineered as a CD8+ T cell-selective IL-2 by combining a reduced-potency IL-2 variant with an anti-CD8β antibody, creating a targeted delivery mechanism that directs immune activation precisely where it’s needed.

The innovation addresses a fundamental challenge in IL-2 immunotherapy: the tendency of systemic IL-2 to activate multiple immune cell populations indiscriminately, leading to toxicity and reduced efficacy. AB248’s design specifically avoids activating natural killer (NK) cells—which can act as a “pharmacological sink” and contribute to adverse effects—and regulatory T cells (Tregs), which suppress anti-tumor immunity.

Clinical Evidence Supports Differentiated Profile

AB248 is currently undergoing evaluation in a Phase 1a/1b clinical trial across patients with advanced solid tumors, including melanoma, renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC), and squamous cell carcinoma of the head and neck (SCCHN). The trial assesses AB248 both as a standalone treatment and in combination with KEYTRUDA® (pembrolizumab), a leading PD-1 checkpoint inhibitor, in patients previously treated with checkpoint inhibitor therapy.

Early pharmacokinetic and pharmacodynamic data from the ongoing trial demonstrate potent and selective CD8+ T cell activation without significant alterations to Treg or NK cell populations. Notably, the data has revealed initial evidence of anti-tumor activity, accompanied by a generally favorable safety profile—a combination that distinguishes AB248 from earlier-generation IL-2 therapies.

Funding Deployment and Pathway Forward

Asher Bio will deploy the Series C proceeds to expand clinical development of AB248, with a focus on generating tumor response data from monotherapy expansion cohorts and evaluating dose escalation combined with checkpoint inhibitor therapy. These data are expected to provide key insights into the drug’s efficacy and tolerability profiles in a broader patient population.

Jake Simson of RA Capital Management underscored the investment rationale: “Asher’s cis-targeting platform represents a genuinely differentiated approach to immunotherapy, with the potential to overcome significant limitations in existing immune-based treatments. The combination of promising preclinical work and encouraging early clinical signals positions the company well for continued advancement.”

Broader Portfolio and Future Directions

Beyond AB248, Asher Bio’s portfolio includes AB821, a CD8-targeted IL-21 immunotherapy, alongside early-stage programs targeting CAR-T cells, myeloid cells, and CD4+ T cells. Founded by Ivana Djuretic and Andy Yeung with support from Third Rock Ventures, the company continues to build on its proprietary cis-targeting platform—a technology designed to enable selective activation of specific immune cell types while avoiding populations that contribute to toxicity or immune suppression.

The Series C closing represents a validation of this platform approach and positions Asher Bio to deliver potentially transformative treatments for cancer patients who have become resistant to or intolerant of conventional checkpoint inhibitor therapies.