Discovery of Cell-Permeable Macrocyclic CyclinA/B RxL Inhibitors that Demonstrate Antitumor Activity
SOUTH SAN FRANCISCO, CA, March 18, 2026 – Circle Pharma, Inc., a clinical-stage biopharmaceutical company pioneering next-generation targeted macrocycle therapeutics for cancer, today announced upcoming presentations at the American Association for Cancer Research (AACR) Annual Meeting, taking place April 17-22 in San Diego.
Presentations will highlight progress across Circle Pharma’s cyclin inhibitor programs and its MXMO™ platform, including preclinical findings and an oral plenary highlighting early clinical activity for CID-078, a first-in-class, orally bioavailable macrocyclic cyclin A/B RxL inhibitor currently being evaluated in a Phase 1 clinical trial for patients with advanced solid tumors.
Details of the presentations are as follows:
Title: Early clinical activity from the phase 1 evaluation of CID-078, a novel Cyclin A/B-RxL inhibitor, in patients with advanced solid tumors
Session Title: Clinical Trials Plenary Session: New Frontiers in Precision Oncology
Date & Time: Sunday, April 19, 1:00-3:00 p.m. PST
Presenter: Afshin Dowlati, M.D.
Title: Discovery of CID-078, a first-in-class oral macrocycle cyclin A/B-RxL inhibitor, for the treatment of cancers with RB1 loss or hyperactivated E2F
Session Title: New Drugs on the Horizon: Part 3
Date & Time: Monday, April 20, 10:15-11:45 a.m. PST
Presenter: Marie Evangelista, Ph.D.
Title: Orally Bioavailable Peptide Macrocycles Disrupting Intracellular Protein-Protein Interactions: Selective Inhibitors of the RxL-binding Site of Cyclin Family Proteins
Session Title: Chemistry to the Clinic Part 3 of 4: Novel Modalities, Targets, and Mechanisms in Drugging Oncogenic Pathways
Date & Time: Saturday, April 18, 12:30-2:00 p.m. PST
Presenter: Justin Shapiro, Ph.D.
About CID-078, Circle Pharma’s Oral Cyclin A/B RxL Inhibitor Program
CID-078 is an orally bioavailable macrocycle with dual activity blocking protein-protein interactions between both cyclins A and B and key substrates that bind to them via conserved RxL motifs. CID-078 selectively targets tumor cells with oncogenic alterations that cause cell cycle dysregulation, including alterations in the tumor suppressor RB1. In preclinical studies, Circle Pharma’s cyclin A/B RxL inhibitors have been shown to potently and selectively disrupt the protein-to-protein interaction between cyclins A and B and their key substrates and modulators, including E2F (a substrate of cyclin A) and MYT1 (a modulator of cyclin B). Preclinical studies have demonstrated the ability of these cyclin A/B RxL inhibitors to cause single-agent tumor regressions in multiple in vivo models. A multicenter Phase 1 clinical trial (NCT06577987) is currently enrolling patients with advanced solid tumors harboring RB1 alterations.
About Circle Pharma
Circle Pharma is a clinical-stage biopharmaceutical company harnessing the power of macrocycles to develop next-generation targeted therapies for cancer and other serious illnesses. The company’s proprietary MXMO™ platform overcomes key challenges in macrocycle drug development, enabling the creation of intrinsically cell-permeable and orally bioavailable therapies, including for historically undruggable targets. Circle Pharma’s pipeline is focused on targeting cyclins, key regulators of the cell cycle that drive many cancers. The company’s lead program, CID-078, is a cyclin A/B RxL inhibitor in Phase 1 clinical development for patients with advanced solid tumors. Circle Pharma is based in South San Francisco, CA. For additional information, please visit us at circlepharma.com and follow us on LinkedIn and X.
Contacts:
Media:
Josie Butler
1AB
josie@1abmedia.com
Investors:
Matt Clawson
1AB
matt@1abmedia.com
Research describes progress of discovery-stage macrocycles to orally bioavailable compounds targeting E2F-high and G1-S checkpoint-compromised cancers
SOUTH SAN FRANCISCO, CA, March 12, 2026 – Circle Pharma, Inc., a clinical-stage biopharmaceutical company pioneering next-generation targeted macrocycle therapeutics for cancer, today announced publication of research in the Journal of Medicinal Chemistry titled, “Orally Bioavailable Cyclin A/B RxL Inhibitors: Optimization of a Novel Class of Macrocyclic Peptides That Target E2F-High and G1-S-Checkpoint-Compromised Cancers.” The paper is included in the journal’s special issue on Peptide Therapeutics.
The publication builds on the company’s August 2025 Journal of Medicinal Chemistry paper titled, “Discovery of Cell-Permeable Macrocyclic Cyclin A/B RxL Inhibitors that Demonstrate Antitumor Activity,” which described the first cell-permeable macrocyclic cyclin A/B RxL inhibitors and provided initial in vivo proof-of-concept efficacy.
“This publication demonstrates the capability of our MXMO™ macrocycle platform to bring forward orally bioavailable macrocycles against therapeutic targets that have been refractory to small molecule chemistry,” said James Aggen, Ph.D., vice president of medicinal chemistry at Circle Pharma. “Our earlier work established that the cyclin A/B hydrophobic patch was druggable with macrocycles. This new research demonstrates these molecules can be delivered orally with compelling in vivo activity.”
Cyclins A and B regulate cell cycle progression by recruiting substrates through an RxL-mediated interaction. In cancers characterized by RB1 loss or elevated E2F activity – including nearly all small-cell lung cancers – this pathway becomes dysregulated, driving uncontrolled tumor growth. Rather than inhibiting CDK catalytic activity, Circle Pharma’s approach disrupts the protein-protein interactions between cyclins A and B and their RxL-containing substrates, selectively killing E2F-high tumor cells.
CID-078, Circle Pharma’s oral cyclin A/B RxL inhibitor is currently being evaluated in a multi-center Phase 1 clinical trial in patients with advanced solid tumors (NCT06577987).
About Circle Pharma
Circle Pharma is a clinical-stage biopharmaceutical company harnessing the power of macrocycles to develop next-generation targeted therapies for cancer. The company’s proprietary MXMO™ platform overcomes key challenges in macrocycle drug development, enabling the creation of intrinsically cell-permeable and orally bioavailable therapies, including for historically undruggable targets. Circle Pharma’s pipeline is focused on targeting cyclins, key regulators of the cell cycle that drive many cancers. The company’s lead program, CID-078, is a cyclin A/B RxL inhibitor in Phase 1 clinical development for patients with advanced solid tumors. Circle Pharma is based in South San Francisco, CA. For additional information, please visit us at circlepharma.com and follow us on LinkedIn and X.
Contacts:
Media:
Josie Butler
1AB
Investors:
Matt Clawson
1AB
SOUTH SAN FRANCISCO, CA, February 17, 2026 – Circle Pharma, Inc., a clinical-stage biopharmaceutical company pioneering next-generation targeted macrocycle therapeutics for cancer, today announced management will participate in upcoming investor conferences in February and March, as follows:
Oppenheimer 36th Annual Healthcare Life Sciences Conference
Presentation Date/Time: 3:20 p.m. ET, Wednesday, Feb. 25, 2026
Participants: David J. Earp, J.D., Ph.D., president and chief executive officer; Anne Borgman, M.D., chief medical officer; Rob Lauzen, chief financial officer
Location: Virtual
TD Cowen 46th Annual Health Care Conference
Date: Monday, March 2, 2026
Participants: David J. Earp, J.D., Ph.D., president and chief executive officer; Anne Borgman, M.D., chief medical officer; Rob Lauzen, chief financial officer
Location: Boston
Leerink Global Healthcare Conference
Date: Wednesday, March 11, 2026
Participants: David J. Earp, J.D., Ph.D., president and chief executive officer; Rob Lauzen, chief financial officer
Location: Miami
About Circle Pharma
Circle Pharma is a clinical-stage biopharmaceutical company harnessing the power of macrocycles to develop next-generation targeted therapies for cancer. The company’s proprietary MXMO™ platform overcomes key challenges in macrocycle drug development, enabling the creation of intrinsically cell-permeable and orally bioavailable therapies, including for historically undruggable targets. Circle Pharma’s pipeline is focused on targeting cyclins, key regulators of the cell cycle that drive many cancers. The company’s lead program, CID-078, is a cyclin A/B RxL inhibitor in Phase 1 clinical development for patients with advanced solid tumors. Circle Pharma is based in South San Francisco, CA. For additional information, please visit us at circlepharma.com and follow us on LinkedIn and X.
Contacts:
Media:
Josie Butler, 1AB
Investors:
Rob Lauzen, Circle Pharma
Robert.Lauzen@circlepharma.com
SOUTH SAN FRANCISCO, CA, January 5, 2026 – Circle Pharma, Inc., a clinical-stage biopharmaceutical company pioneering next-generation targeted macrocycle therapeutics for cancer, today announced that David J. Earp, J.D., Ph.D., president and chief executive officer, will present at the 44th Annual J.P. Morgan Healthcare Conference on Wednesday, January 14, 2026 at 5:00 p.m. PT.
Dr. Earp will provide an overview of the company’s pipeline, including CID-078, a first-in-class oral macrocyclic cyclin A/B RxL inhibitor in Phase 1 clinical development for patients with advanced solid tumors, and CID-165, a first-in-class oral macrocyclic cyclin D1 RxL inhibitor, with potential applications in malignancies, including ER-positive breast cancer and lymphomas.
About Circle Pharma
Circle Pharma is a clinical-stage biopharmaceutical company harnessing the power of macrocycles to develop next-generation targeted therapies for cancer. The company’s proprietary MXMO™ platform overcomes key challenges in macrocycle drug development, enabling the creation of intrinsically cell-permeable and orally bioavailable therapies, including for historically undruggable targets. Circle Pharma’s pipeline is focused on targeting cyclins, key regulators of the cell cycle that drive many cancers. The company’s lead program, CID-078, is a cyclin A/B RxL inhibitor in Phase 1 clinical development for patients with advanced solid tumors. Circle Pharma is based in South San Francisco, CA. For additional information, please visit us at circlepharma.com and follow us on LinkedIn and X.
Contacts:
Media:
Josie Butler
1AB
Investors:
Steve Klass
1AB