Circle Pharma logo

Circle Pharma

Niche

Circle Pharma develops orally deliverable macrocycle drug candidates targeting intracellular protein-protein interactions in cancer; raised $90M Series B in 2023 led by Novo Holdings and Foresite Capital; headquartered in San Francisco;

Best for: Cell-Permeable Macrocycle Oncology Therapeutics
Life Sciences & BioTechCell-Permeable Macrocycle Oncology TherapeuticsWebsiteUpdated May 2026

Company Overview

About Circle Pharma

Circle Pharma is a clinical-stage biopharmaceutical company founded in 2016 by Matthew Jacobson, Siegfried Bhagwati, and Grace Aldrovandi, headquartered in San Francisco, California. The company is developing a new class of therapeutics — cell-permeable macrocycles — designed to inhibit intracellular protein-protein interactions (PPIs) that have historically been considered "undruggable." Protein-protein interactions control critical cellular processes including cell division, apoptosis (programmed cell death), and gene expression. Dysregulation of these interactions drives many cancers, but their large, flat interaction surfaces are difficult to block with small molecules, and biologics (antibodies) cannot cross cell membranes to reach intracellular targets. Circle Pharma's macrocycles are medium-sized ring-shaped molecules engineered to be both cell-permeable and orally bioavailable — a combination rarely achieved — enabling them to reach and inhibit these targets.

Business Model & Competitive Advantage

Circle Pharma combines structure-based drug design with advanced synthetic chemistry to design macrocycles that adopt the three-dimensional shape required to bind specific PPI interfaces. The company's platform systematically generates candidate molecules with drug-like properties: oral bioavailability, cellular permeability, metabolic stability, and selectivity. Its lead programs target intracellular oncology pathways including the MDM2-p53 interaction (relevant to a broad range of cancers) and other PPI targets identified through its structure-biology engine. Unlike kinase inhibitors (the dominant class of cancer targeted therapy), PPI inhibitors can potentially target transcription factors and scaffolding proteins involved in the earliest stages of cancer development.

Competitive Landscape 2025–2026

Circle Pharma raised a $90M Series B in 2023 led by Novo Holdings (the investment arm of the Novo Nordisk Foundation) and Foresite Capital, with participation from Atlas Venture, Novartis Venture Fund, and other investors. This brings total funding to over $130M. The company is advancing its lead candidates toward investigational new drug (IND) applications and initial clinical studies, with ambitions to bring orally delivered PPI inhibitors into cancer clinical trials — a milestone that would validate the macrocycle therapeutic modality for intracellular oncology.

Founded
2016
Headquarters
San Francisco
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