An Open-Label, First-in-Human, Phase I Trial of Daily Pclx-001

Background:

Myristoylation regulates numerous membrane-bound signal transduction pathways important in cancer biology. This modification is catalyzed by N-myristoyltransferases 1 and 2 (NMT1 and NMT2). PCLX-001 is an oral small molecule with high affinity for both NMT proteins (IC50 of 5nM and 8nM, respectively) with high bioavailability and drug-like pharmacokinetic properties. In ex vivo sensitivity screening cell lines of hematologic cancer origin were exquisitely sensitive to PCLX-001, although high sensitivities and cell killing were also seen in some solid tumor lines derived from lung, pancreas, breast, colon, and bladder carcinomas. PCLX-001 demonstrated strong preclinical single-agent antitumor activity and tolerability in vivo in subcutaneous tumor xenograft models derived from lymphoma cell lines, lung cancer cell lines, a breast cancer cell line, as well as in a patient derived xenograft model from a patient with refractory DLBCL. The primary objective of this study is to determine the MTD and/or recommended phase II dose, safety, tolerability, and pharmacokinetics of PCLX-001 as a single agent, in patients with refractory lymphomas and advanced solid tumors. The secondary objective of the study is to evaluate the preliminary single agent anti-tumor activity of PCLX-001 in the patient populations studied.

Methods:

We are now accruing to a multicenter, open-label, phase I dose-escalation study of oral PCLX-001 comprised of two parts (dose escalation and dose expansion). Eligible patients will have: histologically-confirmed advanced solid tumor or B-cell lymphomas who have failed prior therapy and/or are not eligible for therapies; ages ≥ 18 years; adequate organ function; life expectancy of at least 12 weeks; and measurable disease. Part A (dose-escalation) patients will be accrued in cohorts of 3 to 6 patients to each dose level, starting at 20 mg daily on a 28 day cycle. Dose escalation will follow a modified Fibonacci design such that the magnitude of escalation decreases as the dose level nears the human equivalent dose of the highest non-severely toxic dose in dogs and then escalate at 1.4 times the previous dose. Dose escalation and determination of the maximum tolerated dose will be based on the occurrence of dose limiting toxicities in cycle 1. Part B will have two single agent expansion cohorts (n = 20 each) in advanced solid malignancies and relapsed/refractory B-cell lymphoma, to determine the preliminary clinical activity of PCLX-001 to determine the recommended phase II dose.

Results:

Updated study results will be presented, summarizing the outcomes in the preliminary dose cohorts.