Perspective Therapeutics, Inc. ( CATX ) is down 13% at $11.53 at last check Friday.

The downtrend comes as initial results from its study of [212Pb]VMT01 are set to be presented to the International Congress of the Society for Melanoma Research.

VMT01 is a MC1R-targeted radiopharmaceutical therapy (RPT) that can be radiolabeled with either 203Pb for patient selection and dosimetry assessments or 212Pb for alpha particle therapy.

In preclinical experiments [212Pb] VMT01 demonstrated efficacy via direct cell killing at high radiation doses and through immunostimulatory low-dose induction of immune-mediated cell death.

Efficacy was augmented by immune checkpoint inhibitors (ICIs).

Three patients were enrolled in Cohort 1, while seven were enrolled in Cohort 2.

Patients in each cohort received a median of five prior lines of systematic therapy.

No dose-limiting toxicities were observed among any patients, and no adverse events led to treatment discontinuation. Treatment-emergent adverse events (TEAEs) were mostly Grades 1 and 2; there were no Grade 4 or 5 TEAEs.

No renal toxicities have been reported to date.

All patients in Cohort 1 completed three treatments, with one patient experiencing a RECIST version 1.1 objective response and two patients experiencing stable disease at nine and 11 months from the start of treatment, respectively.

In Cohort 2, patients progressed after either the first cycle (3 patients) or the second cycle (4 patients).

The Safety Monitoring Committee (SMC) has reviewed these findings. The SMC recommended exploring a lower dose level of 1.5 mCi per dose, which is lower than the dose administered in Cohort 1, both as a single agent and combined with the anti-PD-1 antibody, Bristol Myers Squibb & Co ( BMY ) Opdivo (nivolumab).

The SMC recommendation would allow for the monotherapy and combination cohorts to proceed concurrently.

An amendment to further explore lower dose levels for monotherapy is planned. The combination cohort at 1.5 mCi per dose with nivolumab is active and now open for enrollment.

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