Topical Histone Deacetylase Inhibitor Reduced BCC Size in Phase 2 Study

Jeff Craven

June 14, 2021

In the first clinical trial of a topical histone deacetylase (HDAC) inhibitor, remetinostat showed clinical efficacy across several basal cell carcinoma (BCC) tumor types, according to research presented at the annual meeting of the Society for Investigative Dermatology.

"Our results demonstrate a clinically significant decrease in tumor size in response to 6 weeks of topical 1% remetinostat therapy in 70% of per-protocol tumors, with 55% reaching complete pathological resolution," James M. Kilgour, MD, a postdoctoral research fellow at the Sarin Lab at Stanford (Calif.) University, said at the meeting.

Surgical excision is the preferred treatment for BCC, but there is still a need for noninvasive treatment options, Kilgour said. "Given the potential morbidity associated with excision, particularly for patients experiencing multiple or recurrent tumors, such as the immunosuppressed or patients with Gorlin syndrome, an effective and tolerable topical therapy would be a significant benefit," he noted.

Previously, in an in silico screen experiment, Kilgour and colleagues identified HDAC inhibitors as a "top predicted therapeutic" for BCC treatment, and found that in mice studies, HDAC inhibitors were able to suppress the growth of BCC cell lines and BCC allografts.

Remetinostat, a pan-HDAC inhibitor, is being investigated as a treatment for cutaneous T-cell lymphoma.

HDAC inhibitors are thought to "alter expression of key oncogenes and tumor suppressors through epigenetic modification of histone and nonhistone proteins," he noted.

To evaluate the efficacy of topical remetinostat for BCC, the investigators enrolled 30 patients with 49 BCC tumors in a phase 2, open-label, single-arm trial. Participants had tumors that were greater than 5 mm in diameter and had been referred to surgery at Stanford before enrollment. Patients were a mean of 59 years old, 63% were men, and 90% were White; 59.2% of participants had tumors with a diameter greater than 10 mm, the rest had tumors with a diameter of 10 mm or less.

After the tumors were photographed and measured, participants received 6 weeks of topical remetinostat therapy, followed by final measurement and photography of the tumors at 8 weeks and surgical excision. Topical remetinostat 1% gel was applied three times per day under bandage occlusion.

Overall, 25 participants with 33 tumors were included in the per-protocol analysis. At 8 weeks, there was at least a 30% decrease in diameter from baseline for 69.7% of tumors in these patients, with 17 of 33 tumors showing a complete response by week 8.

Regarding tumor subtypes, there was a 100% overall response rate for the 6 superficial BCC tumors (1 partial response, 5 complete responses), a 68.2% ORR for the 22 nodular tumors (5 partial responses, 10 complete responses), and a 66.7% ORR for the 3 infiltrative tumors (no partial responses, 2 complete responses). There were no partial or complete responses for the two micronodular tumors.

Most adverse events in the study were localized drug reactions, with no serious or systemic adverse events, Kilgour noted, with 10 tumors demonstrating either no reaction or a grade 1 reaction, and 23 tumors having a grade 2 or grade 3 response.

The investigators also used imaging (ImageJ) software to evaluate the average decrease in cross-sectional tumor area. The results of the analysis showed an average decrease at 8 weeks from baseline of 71.5%. In addition, histological assessment at 8 weeks demonstrated that 54.8% of tumors had complete pathological resolution.

"In the future, we advocate for a follow-up blinded, randomized, controlled trial of remetinostat with greater participant diversity," Kilgour said. "Specifically, greater power is needed to understand which histological subtypes of BCC will respond best to the treatment and we need to understand the long-term durability of tumor resolution."

Remetinostat Promising as Topical BCC Therapy

In an interview, Beth G. Goldstein, MD, a dermatologist and Mohs surgeon in Chapel Hill, N.C., noted that the preliminary study was "an exciting report of a safe, well-tolerated nonsurgical option for patients with superficial BCCs on the trunk and extremities," which has potential to be used in the future for nonsuperficial BCCs. The study shows that superficial BCCs can respond at a rate of 100% on nonfacial areas, said Goldstein, who was not involved in the research. "These lesions can be quite large with higher chances of recurrence and difficulty with wound care.

"This type of directed therapy hopefully continues to be perfected for treatment of BCC that avoids scarring and is well tolerated," she added.

Goldstein commented that complete pathological resolution of 54.8% "was still unacceptably low for the remaining tumor types." For those cases, she said remetinostat could possibly "provide a topical option as an adjunctive treatment for potentially reducing the size of the BCC prior to surgical removal," as an alternative to a systemic therapy like vismodegib (Erivedge).

Goldstein said the strengths of the study were in the variety of tumors, close follow-up with histologic evaluation and safety signals. In terms of limitations, she said whether there were any cases of Gorlin syndrome was not clear. In addition, at least 30% of BCCs have a mixed tumor type on Mohs surgery that differs from the original biopsy, and "there was no mention if the residual tumor remained with the same histology," she said.

In the future, a large, randomized trial is warranted to stratify for Gorlin syndrome, patients who are immunosuppressed, and additional tumor types that were underrepresented in this study, such as micronodular tumors, Goldstein said. Future studies also should examine how remetinostat impacts BCC in facial areas, the effect of multiple applications, and how the therapy performs as an adjunctive treatment before surgery.

This study was funded by Medivir, the Damon Runyon Foundation, National Cancer Institute, an American Skin Association Hambrick Medical Student grant, and Stanford Medical Scholars. Kilgour and Goldstein reported no relevant financial disclosures.

This article originally appeared on, part of the Medscape Professional Network.


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