Provectus Biopharmaceuticals, Inc. provided updated data from an ongoing Phase 1b/2 clinical trial of investigational cancer immunotherapy PV-10 (rose bengal sodium) in combination with standard of care immune checkpoint blockade (CB) for the treatment of advanced cutaneous Melanoma (NCT02557321). Initial results from CB-naive patients in the main study cohort illustrated potential clinical benefit across all stages of metastasis. Longer-term follow-up of an expanded patient population has been assessed.

Participants must have had at least 1 injectable lesion and at least 1 measurable target lesion and been a candidate for pembrolizumab. The combination of PV-10 and pembrolizumab was administered every 3 weeks for up to 5 cycles, followed by pembrolizumab alone every 3 weeks for a total duration of up to 24 months. Patients may have received PV-10 as needed (PRN) beyond the initial treatment course per investigator discretion.

The primary endpoint of the Phase 1b portion was safety and tolerability. Objective response rate (ORR) and progression-free survival (PFS) were key secondary endpoints (assessed via RECIST 1.1 after 15 weeks, and then every 12 weeks). The addition of an expansion cohort balanced overall enrollment at 25 patients: Median age 73.0 years, range 28-82, 20 male (80%), 5 female (20%), and 6 Stage IIIB-IIIC (24%), 8 Stage IV M1a (32%), 7 M1b (28%), 4 M1c (16%) per the American Joint Committee on Cancer (AJCC) melanoma staging system.

Treatment-emergent adverse events were consistent with the established patterns of both study drugs. There was no evidence of overlap. For all CB-naïve patients: ORR was 72%; 20% complete response (CR) and 52% partial response (PR), edian PFS (mPFS) was 12.5 months for all patients, Median overall survival (mOS) was 37.6 months (3.1 years), and Median disease-specific survival (mDSS) was 64.4 months (5.4 years).

For CB-naïve Stage III patients: ORR was 83%; 50% CR and 33% PR, CRs were rapid and durable, having been reached within 15 weeks by 2 patients and within 27 weeks by the third, and are ongoing after 24-44 months of follow-up, mPFS has not been reached, mOS is estimated to be 36.3 months (3.0 years), mDSS is estimated to be 42.5 months (3.5 years), and Both survival metrics could be affected by the status of the last patient in the cohort who is an ongoing complete responder at 30.1 months (2.5 years).