Commentary Open Access
Volume 2 | Issue 3 | DOI: https://doi.org/10.33696/haematology.2.032

Unesbulin – a Novel Anti-tubulin Cancer Therapeutic

  • 1PTC Therapeutics, Inc. South Plainfield, NJ, 07080, USA
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Corresponding Author

Ronald Kong, rkong@ptcbio.com

Received Date: April 29, 2021

Accepted Date: May 28, 2021


Unesbulin (also known as PTC596) is novel tubulin binding drug being developed for the treatment of cancers. The drug binds to the tubulin colchicine binding site to block tumor growth by inhibiting microtubular formation leading to mitotic G2/M phase cell arrest and cell death. Importantly, in contrast to the majority of other tubulin binding compounds, unesbulin is not a substrate for p-glycoprotein transporter and can be administered orally as a tablet. Preclinical studies indicate that the drug has activity both against solid tumor and haemotologic cancers. A recently completed phase 1 study evaluated the safety and pharmacokinetics (PK) of unesbulin in subjects (aged = 18 years [N=31]) with advanced solid tumors. Patients received eight doses per 4-week cycle schedule, and doses were escalated from 0.65, 1.3, 2.6, 5.2, 7.0, to 10.4 mg/kg. Unesbulin was rapidly absorbed and for doses between 0.65 and 7.0 mg/kg reached a maximum plasma concentration 2 to 4 hours after dosing. Area under the plasma concentration–time curve increased proportionally with body weight–adjusted doses and no accumulation occurred after multiple administrations up to 7.0 mg/ kg. For all doses, unesbulin had a terminal half-life ranging from 12 to 20 hours. Overall, unesbulin was well tolerated. The incidences of neutropenia and thrombocytopenia were low; only one patient treated with 10.4 mg/kg experienced dose-limiting toxicity of neutropenia and thrombocytopenia, both of which were reversible. These data support the further development of unesbulin in treating cancers. Currently, several ongoing clinical trials are investigating the drug in other cancers including in women with ovarian cancer, in patients with advanced leiomyosarcoma, and in children with diffuse intrinsic pontine glioma and high-grade glioma.

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