Octagon Therapeutics

Octagon Therapeutics, Inc. was a preclinical-stage biotechnology company working on medicines for autoimmune and inflammatory diseases. Its approach centered on glyco-immune checkpoint receptors: immune cells carry checkpoint receptors that normally prevent them from attacking healthy human cells, and in conditions such as systemic lupus erythematosus, multiple sclerosis, Sjogren's syndrome and myositis these checkpoints are disrupted. Octagon aimed to restore receptor activity in order to re-establish immune homeostasis without broadly suppressing the immune system, using insights into the glycoproteome to identify disease-driving biology.

The company's programs focused on resetting B cell homeostasis by modulating key regulatory receptors, with potential application in vasculitis, cutaneous lupus and multiple sclerosis, either as monotherapy or in combination with existing therapies. Its most advanced molecule, OCT-50, was designed to suppress autoreactive B cells by restoring the natural regulatory role of Siglec-2 (CD22) and was at preclinical stage with indications including cutaneous lupus erythematosus. A second program, OCT-102, targeted CD8 for dermatomyositis at discovery stage, and a cardiometabolic discovery program was associated with both Octagon and Novo Nordisk.

Octagon was founded in 2017 on scientific insights developed at Harvard, with early work on selective immunomodulation for autoimmune disease also arising from research by Dr. Eleftherios Mylonakis at Brown University and Rhode Island Hospital. The company was headquartered in Providence, Rhode Island, with laboratory space at The Engine in Cambridge, Massachusetts, and reported headcount in the 10-50 range. It wound down operations in 2025.

Founding story

Octagon was founded in 2017 on scientific insights developed at Harvard by a team that included Isaac Stoner as co-founder and CEO and Fred Ausubel, Professor of Genetics at Harvard Medical School (Emeritus), as co-founder and founding CSO. Initial efforts on new medicines for autoimmune disease based on selective immunomodulation arose from the work of Dr. Eleftherios Mylonakis, the Charles C.J. Carpenter Professor of Infectious Disease at Brown University and Chief of Infectious Diseases at Rhode Island Hospital and the Miriam Hospital. Several team members, including Stoner and VP of Biology Brent Cezairliyan, were Brown University graduates.

Business model

Octagon operated as a venture-backed preclinical drug developer, advancing proprietary immunomodulatory molecules through discovery and preclinical stages while also offering discovery partnership opportunities to other organizations, as reflected in its research alliance with Novo Nordisk.

No product revenue was reported; the company was financed through equity funding rounds and pursued discovery partnerships such as its alliance with Novo Nordisk.

Traction

Octagon reported preclinical-stage programs (OCT-50 preclinical; OCT-102 and a Novo Nordisk-linked cardiometabolic program at discovery), a 2022 research alliance with Novo Nordisk, a Series Seed round led by Slater Technology Fund in April 2024, and a headcount in the 10-50 range before winding down in 2025.

Latest developments

In April 2025, Fierce Biotech reported that Octagon was winding down, with CEO Isaac Stoner citing the deprioritization of the lead B cell immunomodulator program and unresolved biology questions around another high-potential pipeline effort. In November 2025, Stoner was appointed CEO of MindImmune Therapeutics, with his biography noting he co-founded and led Octagon from 2017 to 2025.