Asher Bio

Asher Biotherapeutics, Inc. (Asher Bio) is a South San Francisco-based biotechnology company developing precisely targeted immunotherapies for cancer, autoimmune disease and chronic viral/infectious disease. Its proprietary "cis-targeting" approach fuses a modified immunomodulatory protein, such as a cytokine with reduced receptor potency, to a targeting antibody, so that the immunomodulatory receptor is engaged only when the targeting antigen is present on the same cell. The stated aim is to overcome the pleiotropy of conventional cytokine therapies, which act on many immune cell types at once, by activating only the cell type that drives the desired therapeutic effect while limiting antagonistic and toxic effects from other cell types.

The lead program is etakafusp alfa (formerly AB248), a CD8+ T cell-selective interleukin-2 generated by fusing a reduced-potency IL-2 mutein to an anti-CD8-beta antibody. It is engineered to activate and expand CD8+ effector T cells while avoiding natural killer cells, which can act as a pharmacological sink and contribute to toxicity, and regulatory T cells, which are immunosuppressive. Etakafusp alfa is in an open-label Phase 1a/1b dose-escalation and expansion study (NCT05653882) as monotherapy and in combination with KEYTRUDA (pembrolizumab) in patients with recurrent locally advanced or metastatic solid tumors, including melanoma, renal cell carcinoma, non-small cell lung cancer and squamous cell carcinoma of the head and neck, previously treated with a PD-1 or PD-L1 checkpoint inhibitor. The company reports initial pharmacokinetic and pharmacodynamic data showing selective CD8+ T cell activation without substantial changes in Treg and NK cell numbers, initial evidence of anti-tumor activity and a generally well-tolerated safety profile.

Beyond the lead asset, the pipeline includes AB821, a CD8-targeted IL-21 intended to activate CD8+ T cells through a pathway complementary to IL-2, plus early-stage programs directed at CAR-T cells, myeloid cells and CD4+ T cells. The company states that preclinical proof of concept has been established for eight molecules spanning five immune agonists across four cell types, and that it is exploring strategic collaborations to access capabilities outside its core focus areas.

Founding story

Asher Bio was founded by Ivana Djuretic and Andy Yeung with support from Third Rock Ventures, and is located in South San Francisco. Before founding the company, Djuretic was Head of Cytokine Biology in Pfizer's Cancer Immunology Discovery Unit, and previously held roles at Celgene and Tempero Pharmaceuticals; she holds a PhD in immunology from Harvard University. The company's name derives from ancient Hebrew, where "Asher" means happy, blessed and fortunate, reflecting its stated mission around patient outcomes.

Business model

Clinical-stage biotechnology company funded by venture and institutional investors, developing proprietary drug candidates internally and pursuing strategic collaborations, including clinical trial collaboration and supply agreements, to extend its platform.

Traction

Etakafusp alfa has advanced into an ongoing Phase 1a/1b dose escalation and expansion trial (NCT05653882) with initial data reported as showing proof of mechanism, selective CD8+ T cell activation, early anti-tumor activity and a generally well-tolerated safety profile. Preclinical proof of concept is reported for eight molecules across five immune agonists and four cell types. Two presentations on the CD8-targeted cytokine pipeline were announced for the ASCO 2026 Annual Meeting.

Latest developments

In January 2025 the company announced a clinical trial collaboration and supply agreement to study etakafusp alfa in combination with a bispecific T-cell engager in patients with small cell lung cancer. In May 2026 it announced two presentations at the ASCO 2026 Annual Meeting covering clinical progress across its CD8-targeted cytokine pipeline. AB248 has been assigned the international nonproprietary name etakafusp alfa.