Processa Pharmaceuticals, Inc. announced the successful completion of the safety tolerability evaluation in its Phase 1b trial of Next Generation Capecitabine (NGC-Cap). From the Phase 1b data, two dosage regimens have been selected for the Phase 2 trial. The Phase 2 trial will be in advanced or metastatic breast cancer given FDA?s agreement that the Phase 1b data can be used to support the design of the Phase 2 trial in breast cancer.

NGC-Cap is PCS6422 administered in combination with capecitabine, a precursor of the cancer drug 5-FU. PCS6422 is administered as a single dose 12-24 hours prior to receiving seven days of capecitabine followed by seven drug-free days. The NGC-Cap Phase 1b trial evaluated capecitabine doses from 75 mg once a day (QD) to 225 mg twice a day (BID).

The 5-FU drug exposure for the 18 total patients that received NGC-Cap treatment across four different dosing regimens was 2-10 times that of FDA-approved capecitabine. Sixteen of these patients received at least two cycles of NGC-Cap with the other two patients discontinuing treatment before completing two cycles because of progressing disease. Four of the 16 patients are still receiving treatment in the study.

At this time, only one of the 16 patients (6%) has experienced a mild case of hand-foot-syndrome (HFS), a side effect associated with the 5-FU metabolite fluoro-beta-alanine (FBAL). This lower incidence of HFS was expected given PCS6422 inhibits the metabolism of 5-FU to FBAL. The 6% incidence of HFS differs from the incidence reported for FDA-approved capecitabine, where greater than 50% of patients on capecitabine developed HFS and greater than 10% of the patients developed severe HFS.

The incidence of myelosuppression in patients on the high dose of NGC-Cap (225 mg BID) is currently approximately 71%, with more severe myelosuppression occurring in approximately 57% of the patients. The overall myelosuppression incidence rate after patients received the high dose of NGC-Cap is comparable to the 80% rate reported in the capecitabine label. As expected, given the greater 5-FU exposure, the incidence rate of more severe myelosuppression after the high dose of NGC-Cap was greater than the 3% rate reported for capecitabine.

For the lower NGC-Cap dose of 150 mg BID, which also has a greater 5-FU exposure than capecitabine, the incidence of myelosuppression (33%) and more severe myelosuppression (0%) was lower for NGC-Cap compared to capecitabine. Although the primary objective of the Phase 1b trial in patients with advanced gastrointestinal (GI) cancer was not to evaluate efficacy, the Phase 1b trial was designed to provide some preliminary data on efficacy. At this time, of the 11 cancer patients receiving one of the two highest doses of NGC-Cap, five have completed an efficacy evaluation at this time, and four of these five patients (or 80%) showed a positive response.

One of these four patients had a partial response, and three patients demonstrated stable disease. Two patients receiving the highest dose will potentially become eligible for an efficacy evaluation by the end of the first quarter of 2024. Of the remaining four patients in the two highest doses, two dropped out prior to their evaluation because of disease progression and two dropped out because of side effects.