Financing led by The Column Group with participation from Nextech Invest, RA Capital Management, Euclidean Capital and a strategic investment from Eli Lilly and Company
CID-165, a first-in-class oral macrocyclic cyclin D1 RxL inhibitor, is expected to enter clinical development in Q1 2027 for patients with ER+ breast cancer
CID-165 has demonstrated robust anti-tumor activity in cyclin D1-driven preclinical cancer models, including in combination with CDK4/6-dual inhibitors, CDK4-selective inhibitors and endocrine therapies
SOUTH SAN FRANCISCO, CA, September 16, 2026 – Circle Pharma, Inc., a clinical-stage biopharmaceutical company pioneering next-generation targeted macrocycle therapeutics for cancer, today announced an oversubscribed $92.5 million Series E financing. The financing was led by The Column Group and included participation from other existing and new investors including Nextech Invest, RA Capital Management, Euclidean Capital and Eli Lilly and Company. Proceeds from the financing will drive the advancement of CID-165, a first-in-class oral macrocyclic cyclin D1 RxL inhibitor, through early clinical development for ER-positive breast cancer, while also supporting the continued development of Circle Pharma’s broader pipeline of cyclin-targeted macrocycles.
“This financing marks a significant milestone as we execute upon our vision of harnessing the power of macrocycles to transform the treatment of cancer,” said David J. Earp, J.D., Ph.D., president and chief executive officer of Circle Pharma. “Momentum around our cyclin D1 program has continued to build as CID-165 advances toward the clinic. We believe CID-165 has the potential to become a new backbone therapy for ER-positive breast cancer and this financing provides us with the resources to generate meaningful clinical data to validate that potential. Progress across our pipeline underscores the ability of our platform to generate first-in-class compounds across the previously undrugged family of cyclins, the master regulators of the cell cycle. We are grateful for the commitment and support of our existing and new investors.”
“Cyclin D1 is a well-established driver of cancer, especially in ER-positive breast cancer where there is a lineage dependency on this cyclin, but directly targeting it has remained a longstanding challenge,” said Marie Evangelista, Ph.D., chief scientific officer at Circle Pharma. “CID-165 is designed to selectively disrupt the interaction between cyclin D1 and retinoblastoma protein, providing a novel approach to directly targeting this fundamental driver of tumor growth. The robust activity we have observed across preclinical models in ER-positive breast cancer, both as a monotherapy and in combination with established treatments, gives us strong conviction in the potential of CID-165 as we prepare to advance the program into the clinic in the first quarter of 2027.”
About Cyclin D1 and CID-165
Cyclin D1 is a regulatory protein that plays a crucial role in cell cycle progression and is dysregulated in some malignancies, including ER-positive breast cancer and certain lymphomas. In these cancers, dysregulated cyclin D1 drives abnormal cell proliferation through its inactivation of the tumor suppressor retinoblastoma protein (Rb) leading to uncontrolled cell division. In preclinical studies, CID-165 has been shown to potently and selectively disrupt the cyclin D1-Rb interaction allowing Rb to remain active and suppress cancer cell proliferation. CID-165 is a first-in-class, orally bioavailable, macrocyclic cyclin D1 RxL inhibitor that has demonstrated robust anti-tumor activity in cyclin D1-driven preclinical cancer models, including in combination with other therapies such as CDK4/6-dual inhibitors, CDK4-selective inhibitors and endocrine therapies.
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. Circle Pharma’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. 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