Cylene Pharmaceuticals

About Cylene Pharmaceuticals

Cylene Pharmaceuticals, Inc. operated as a clinical-stage biopharmaceutical firm, directing its efforts toward the discovery and development of small-molecule drugs for oncology. The company was established in 1997, initially as Cyternex, Inc., before rebranding to Cylene Pharmaceuticals in October 2003. Throughout its existence, Cylene was a privately held entity headquartered in San Diego, California. The company ceased operations around April 2013.

The company's core focus was on developing targeted drugs aimed at newly validated cancer pathways. Cylene's proprietary drug discovery platform, known as STAND (Selective TArgeting of Non-Oncogene Networks in Disease), produced a portfolio of drug candidates. A key area of its research was inhibiting ribosomal RNA (rRNA) biogenesis, a process amplified in cancer cells, through its RABIT™ (Ribosomal RNA Biosynthesis Inhibition Technology) platform. This approach aimed to activate the p53 tumor suppressor gene to induce cancer cell death through a non-genotoxic mechanism, a method designed to avoid the side effects of direct DNA damage. The company also explored CK2 pathways to enable rational drug combinations for various cancer types.

Cylene's pipeline included several drug candidates. Its most advanced product, CX-3543, also known as Quarfloxin, was a Ribosomal RNA Biogenesis Inhibitor that reached Phase II clinical trials for multiple cancers. Another significant candidate was CX-4945 (Silmitasertib), a first-in-class, orally administered CK2 inhibitor that entered Phase I trials for multiple myeloma and solid tumors. A third molecule, CX-5461, was developed as a selective inhibitor of the RNA Polymerase I (Pol I) cancer target for treating leukemias, lymphomas, and multiple myeloma.

The company's business model relied on venture capital funding to advance its drug candidates through the clinical trial phases. Cylene successfully raised approximately $106 million over several funding rounds from a consortium of investors. Notable financing events include a $44 million Series C round in 2007, co-led by HBM BioVentures and Lilly Ventures, and multiple Series D rounds. In 2013, Cylene entered into an exclusive option and license agreement with TetraGene LLC for the development of Quarfloxin and its associated technologies. Following Cylene's closure, the rights to Silmitasertib (CX-4945) were acquired by Senhwa Biosciences.