Romidepsin

In plain language

Romidepsin is a cancer drug for certain T-cell lymphomas, sold as Istodax. It is a small bicyclic molecule made by soil bacteria that blocks a family of enzymes controlling how tightly DNA is packed.

When the packing loosens, genes that tell cancer cells to stop dividing can switch back on. It is given by IV infusion over four hours on three days a week, once every four weeks. One of its two approved uses was withdrawn in 2021 after a follow-up trial failed; the other remains, and generics are available.

For students

Romidepsin is a bicyclic depsipeptide (about 541 Da) from Chromobacterium violaceum, discovered by Fujisawa researchers in the 1990s. It is a prodrug: intracellular reduction of its disulfide bond reveals a thiol that chelates zinc at the active site of histone deacetylases (class I HDACs), inhibiting deacetylation and allowing transcription of cell-cycle arrest and apoptosis genes.

Approved in 2009 for cutaneous T-cell lymphoma (CTCL) on the basis of two single-arm trials (71 and 96 patients, response rates about 34-35%), and in 2011 for peripheral T-cell lymphoma (PTCL), the PTCL indication was voluntarily withdrawn in 2021 after the confirmatory phase 3 trial (Romidepsin in PTCL, FORESEE or equivalent) failed to validate benefit. Its side-effect profile (nausea, vomiting, fatigue, infections, ECG T-wave changes requiring potassium and magnesium monitoring) reflects class-wide HDAC inhibition.

For researchers and instructors

Biochemistry. A prodrug mechanism activated by intracellular glutathione reduction is distinctive among approved drugs, and its zinc-chelating pharmacophore is shared with synthetic HDAC inhibitors (vorinostat, belinostat).

Pharmacology. Half-life about 3 hours, metabolized by CYP3A4 with strong interactions with azole antifungals and rifampin; dose modifications for toxicity; CTCL response durability (median about 15 months in responders) is the labeled differentiator.

Human evidence. Two single-arm pivotal CTCL trials (overall response 34-35%, complete responses in about 6%); PTCL approval was converted to withdrawal in 2021 after the confirmatory trial failed, a regulatory teaching case under the accelerated approval framework.

Teaching point. Teaches the accelerated-approval lifecycle: single-arm evidence, surrogate endpoints, and the rare completed withdrawal when confirmatory trials fail.