Bcl-2 and bcl-XL are anti-apoptotic proteins that promote drug resistance and enhance tumor cell survival. Bcl-2 gene amplification occurs in 90% of cutaneous melanomas implicating it as a potential target. PNT100 is a 24-mer unmodified DNA oligonucleotide complementary to a non-coding region of bcl-2. PNT2258, is comprised of PNT100 encapsulated in a unique pH tunable nuclear-targeted liposomes termed SMARTICLES®. Preliminary studies demonstrated fluorescently-labeled PNT100 in a SMARTICLE® is delivered to the cell nucleus and that PNT2258 produces dramatic tumor regression in a diffuse large cell lymphoma xenograft, prolonging survival with a coincident decrease in bcl-2 protein. PNT2258 activity in the A375 melanoma model was assessed as a single agent or in combination in two separate studies. Study 1: PNT2258 alone, IV, 5 days/week for 3 weeks, to mice bearing A375 produced growth delays of 10.4, 7.8, and 7.8 days at 12.5, 8.3, and 5.6 mg/kg/dose, respectively. Docetaxel alone, IV weekly x3, produced growth delays of 19.4 (1/10 TFS), 14.8 (1/10 TFS), and 11.5 days at 30, 20, and 13.3mg/kg/dose. Combination therapy produced growth delays of 45.3 (5/10 TFS), 18.9, 28.1 (2/10 TFS), and 25.0 (3/10 TFS) days at 12.5+30, 12.5+20, 5.6+30, and 5.6+20 mg/kg/dose, respectively. Study 2: PNT2258 alone produced a growth delay of 12 days at 15mg/kg/dose. Dacarbazine alone was ineffective at 80 mg/kg/dose IP. Combination therapy was not superior to PNT2258 alone. In contrast, vemurafenib alone (37.5 mg/kg/dose, PO, BIDx18 days) was highly active producing a growth delay in excess of 30 days, as did the combination of PNT2258+vemurafenib. PNT2258 is currently being evaluated for safety and tolerability in a phase Ia clinical trial. Preliminary mouse and human pharmacokinetics suggest that exposure levels in humans are similar to those producing anti-tumor efficacy in mice. Overall, 1) PNT2258+docetaxel produced a greater than additive effect compared to single agents, 2) PNT2258+dacarbazine was not superior to PNT2258 alone, 3) PNT2258+vemurafenib while highly active, was not superior to vemurafinib therapy alone, and 4) therapeutic PNT2258 exposures have been attained in patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2764. doi:1538-7445.AM2012-2764