Circle Pharma builds macrocyclic peptide drugs for intracellular protein–protein interaction targets — the 'undruggable' space where small molecules struggle and antibodies cannot reach. The lead clinical candidate is CID-078, a cyclin-targeted bicyclic peptide for RB1-deficient tumors.
CID-078 readouts have appeared at AACR 2026 and adjacent venues, with Phase 1 dose-escalation and biomarker work covered on this site. The company's broader pipeline targets cyclin family members and other cell-cycle regulators that have eluded conventional drug discovery.
Stories here cover trial readouts, AACR presentations, and partnership announcements. See #cid-078, #cyclin, #rb1, and #macrocyclic-peptide for adjacent threads.
Circle Pharma presents early clinical data for CID-078 in the AACR 2026 Clinical Trials Plenary (Sunday, April 19, 1:00-3:00 PT). CID-078 is a first-in-class orally bioavailable macrocyclic peptide cyclin A/B RxL inhibitor evaluated in a Phase 1 multicenter trial (NCT06577987) for advanced solid tumors with RB1 alterations. The plenary slot — a coveted showcase for private biotechs — tests whether macrocyclic peptides can establish themselves as a third modality alongside small molecules and biologics.
Circle Pharma presents "Orally Bioavailable Peptide Macrocycles Disrupting Intracellular Protein-Protein Interactions: Selective Inhibitors of the RxL-binding Site of Cyclin Family Proteins" at AACR's Chemistry to the Clinic Part 3 session on Saturday, April 18, 12:30-2:00 p.m. PST. The presentation covers CID-078, an orally bioavailable macrocycle with dual activity blocking cyclin A/B protein-protein interactions, selectively targeting tumor cells with RB1 alterations.
ApexOnco analysis frames AACR 2026 as a breakout moment for private peptide-based biotechs. Circle Pharma (macrocyclic peptides), Bicycle Therapeutics (bicyclic peptide drug conjugates), and SignaBlok (TREM-1 peptide) all landed prominent slots. Antibody-drug and peptide-drug conjugates remain the dominant theme, with conjugate-related abstracts outpacing any other modality in the clinical late-breaker sessions.
Circle Pharma secured a coveted oral plenary slot at AACR 2026 to present early Phase 1 clinical activity data for CID-078, a first-in-class orally bioavailable macrocyclic peptide cyclin A/B RxL inhibitor for patients with advanced solid tumors harboring RB1 alterations. The plenary (Sunday, April 19) validates macrocyclic peptides as viable oral oncology drugs — a major milestone for the modality.