VP-102 shows potential in treating molluscum contagiosum

VP-102, a proprietary, drug-device combination containing cantharidin 0.7% (w/v), was effective and safe for treating molluscum contagiosum (MC), according to the phase III CAMP* trials.

MC is a common viral skin infection predominant in children, immunocompromised individuals, and sexually active adults. [Lancet Infect Dis 2013;13:877-888] MC is classified as self-limiting and benign in immunocompetent individuals; as such, most clinicians resort to waiting for natural clearance of lesions. [PLoS One 2013;8:e76948; Pediatr Dermatol 2006;23:574-579]

However, despite an average of <20 lesions in healthy individuals, these can occasionally present in the hundreds, with widespread distribution. [Arch Dermatol 2012;148:1257-1264] Concomitant atopic dermatitis (AD) may increase lesion count and prolong disease duration. Also, the average duration of MC is usually in years, and there are no FDA-approved treatments, the researchers stressed.

“It is therefore essential [to] have a safe and effective way to treat patients with MC, including those with concomitant AD … [to] alleviate discomfort, risk of auto-inoculation and spread to others, scarring, and social stigma,” they underscored.

Cantharidin – a topical vesicant – has been used to treat MC for more than half a century; however, its limited availability, lack of standard formulation, and variations in concentration, application methods, and treatment durations have contributed to its limited use. [Pediatr Dermatol 2017;34:504-515; J Drugs Dermatol 2020;19:S18-S23]

“[T]he CAMP studies are the first large controlled trials of cantharidin with a consistent formulation, dosing schedule, and method of application for MC treatment … [The findings show that] VP-102 was statistically significantly superior to vehicle in achieving complete clearance of MC lesions at end-of-study (EOS) visit in both trials, with adverse events (AEs) that were generally mild-to-moderate and confined to application sites.”

Participants** (n=528; median age 6 years, 51 percent male) were randomized 3:2 to apply VP-102 or vehicle to all treatable skin lesions every 21 days until complete lesion clearance is achieved or up to four treatments (EOS). [JAMA Dermatol 2020;doi:10.1001/jamadermatol.2020.3238]

At EOS, more VP-102 vs vehicle recipients achieved complete lesion clearance in CAMP-1 (46 percent vs 18 percent) and CAMP-2 (54 percent vs 13 percent; p<0.001 for both).

In terms of lesion reduction at EOS, in CAMP-1, VP-102 reduced lesions (mean, 69 percent) while vehicle led to a 20-percent increase in lesions (p<0.05). In CAMP-2, both arms saw reductions in baseline lesions, but more so with VP-102 than vehicle (mean, 83 percent vs 19 percent; p<0.05).

The superiority of VP-102 to vehicle was already evident by day 21 (after only a single treatment) in CAMP-1 (11 percent vs 4 percent; p=0.03).

Almost all VP-102 recipients reported AEs (99 percent and 95 percent in CAMP-1 and CAMP-2, respectively), but most were mild-to-moderate in severity. The most common AEs were application site vesicles, pain, and pruritus which, according to the researchers, were “well-known, reversible reactions related to the pharmacodynamic response of the skin to cantharidin.”

Discontinuation rate due to treatment-emergent (TE)AEs with VP-102 was low (2 percent), which reflects the tolerability of VP-102 in this paediatric cohort. “AEs potentially associated with infection were reported with a low frequency and were well-balanced between [groups],” they added. There was also no evidence of TEAEs suggestive of systemic absorption of topical cantharidin, as all drug-related TEAEs were confined to the application sites, they said.

“[Taken together,] these trials provide robust efficacy and safety data that support the use of VP-102 for the treatment of MC in participants aged ≥2 years,” said the researchers.

It is not possible however to determine the exact number of treatments necessary to clear an individual lesion, as both studies tracked complete lesion clearance, they pointed out. Also, the studies only allowed a maximum of four treatments, which is in contrast with the recommended continued cantharidin use until complete skin clearance is achieved. [Pediatr Dermatol 2009;26:405-408] The predominantly paediatric cohort may also limit extrapolation of the findings to adults.

Further investigation is thus warranted to ascertain the validity of the findings. It would also be worth looking into the effects of VP-102 in individuals with comorbid AD at or around the lesion sites, they added.