Increased gene expression following increased histone acetylation is an expected effect of an HDAC inhibitor. Increased hemoglobin F (another surrogate marker for gene-expression changes resulting from HDAC inhibition) was also detected in blood after romidepsin administration, and persistent histone acetylation was inversely associated with drug clearance and directly associated with patient response to therapy. Dosage and administration
The approved dosage of romidepsin in both CTCL and PTCL is a four-hour i.v. administration of 14 mg/m2 on days 1, 8, and 15 of a 28-day treatment cycle. This cycle should be repeated as long as the patient continues to benefit and tolerate the therapy. A dose reduction to 10 mg/m2 is possible in some patients who experience high-grade toxicities. Pharmacokinetics
In trials involving patients with advanced cancers, romidepsin exhibited linear pharmacokinetics across doses ranging from 1.0 to 24.9 mg/m2 when administered intravenously over four hours. Age, race, sex, mild-to-severe renal impairment, and mild-to-moderate hepatic impairment had no effect on romidepsin pharmacokinetics. No accumulation of plasma concentration was observed after repeated dosing. Mechanism of action
Romidepsin acts as a prodrug with the disulfide bond undergoing reduction within the cell to release a zinc-binding thiol. The thiol binds to a zinc atom in the binding pocket of Zn-dependent histone deacetylase to block its activity. Thus it is an HDAC inhibitor. Many HDAC inhibitors are potential treatments for cancer through the ability to epigenetically restore normal expression of tumor suppressor genes, which may result in cell cycle arrest, differentiation, and apoptosis. Adverse effects
The use of romidepsin is uniformly associated with adverse effects.
Hypervalinemia is a rare autosomal recessive metabolic disorder in which urinary and serum levels of the branched-chain amino acid valine are elevated, without related elevation of the branched-chain amino acids leucine and isoleucine. It is caused by a deficiency of the enzyme valine transaminase. Presentation
Presenting in infancy, symptoms include lack of appetite, vomiting, dehydration, hypotonia and failure to thrive. Genetics
Hypervalinemia is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder. Diagnosis
See also
Isovaleric acidemia
Maple syrup urine disease
Propionic acidemia

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