Seliciclib (R-Roscovitine)

Seliciclib (R-roscovitine or CYC202) is an investigational oral medicine that Cyclacel is developing to treat Cushing’s disease, as well as several cancers, rheumatoid arthritis (RA), and cystic fibrosis (CF).

How does seliciclib work?

Cushing’s disease is caused by a tumor in the pituitary gland. The tumor stimulates excessive production of the adrenocorticotropic hormone (ACTH), which triggers the production and release of cortisol from the adrenal glands. To produce ACTH, the precursor proopiomelanocortin (POMC) gene is necessary.

Seliciclib is a cell cycle inhibitor that aims to target the tumor in the pituitary gland. It acts to block cyclin-dependent kinase 2 (CDK2) and cyclin E, which regulate cell growth. By inhibiting these two targets, seliciclib may be able to control, or shrink, the pituitary tumor by blocking cell growth.

Cyclin E expression is known to be elevated in Cushing’s disease tumors. Cyclin E plays a role in signaling pathways to produce more POMC, and therefore ACTH. By blocking cyclin E, seliciclib could reduce ACTH and cortisol levels, alleviating the symptoms of Cushing’s disease.

Seliciclib in clinical trials

Cyclacel has carried out 16 clinical trials with seliciclib, demonstrating that it is safe, and well-tolerated by both healthy volunteers and patients with various disorders.

A Phase 2 clinical trial (NCT02160730) aimed to test the effectiveness of seliciclib in normalizing urinary free cortisol levels (a measure of the amount of urinary free cortisol in urine) in Cushing’s patients over a four-week period. However, the grant supporting this trial ran out, and the study was terminated.

A second Phase 2 clinical trial (NCT03774446) is now recruiting up to 29 adults with new, recurrent, or persistent Cushing’s disease at Cedars-Sinai Medical Center in Los Angeles for an open-label study of seliciclib. Patients will be given up to 800 mg of oral seliciclib four days each week for four weeks.

The trial’s primary goals include the number of patients with normalized cortisol levels, as seen by urinary free cortisol measures, after four weeks of treatment. It is due to conclude in November 2022. Contact information for those interested can be found here.

Other information

Previous clinical trials have reported side effects linked to seliciclib’s use. These include nausea, vomiting, fatigue, hypokalemia (low potassium in the blood), and elevated liver enzymes.


Last updated: April 22, 2020


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