FDA approval of Valchlor was based on a randomized, non-inferiority trial in 260 patients with stage IA, IB, or IIA mycosis fungoides comparing it to a 0.02% mechlorethamine compounded ointment, both applied once daily for up to 1 year. Response rates, based on a composite assessment of index lesion severity, were slightly higher with the gel (59% vs. 48%, which met prespecified criteria for noninferiority). Based on a Kaplan-Meier analysis, the estimated time to a 50% response rate was shorter with the gel than with the compounded ointment (26 weeks vs. 42 weeks). It was also estimated that at least 90% of the responses in both treatment arms would be maintained for ≥10 months, the maximum follow-up period in the trial.

No serious drug-related adverse effects were observed, and no systemic absorption of the drug was detected. About 20% of patients treated with the gel and about 17% of those treated with the ointment withdrew from the study because of skin irritation, which has always been the most troublesome side effect of topical mechlorethamine.1

A thin layer of mechlorethamine gel should be applied to each affected area of the skin once daily. The drug should be stopped if skin ulceration, blistering, or moderately severe or severe dermatitis occurs. Treatment can be restarted at a frequency of once every 3 days for 1 week and, if tolerated, can be increased to every other day for another week, and then to once daily. The gel should be stored in the refrigerator and applied within 30 minutes of removing it from the refrigerator. The cost of a 60-g tube is $2900.2