Antitumor efficacy and acute toxicity of the novel dipeptide melphalanyl-p-L-fluorophenylalanine ethyl ester (J1) in vivo

Abstract

The novel alkylating dipeptide melphalanyl-p-L-fluorophenylalanine ethyl ester (J1) was evaluated for acute toxicity and antitumor activity in mice, with melphalan as a reference. To determine a safe and tolerable dose for efficacy studies the acute toxicity following intravenous injection in the tail vein was monitored using a 14-day schedule with up to four doses. The highest tested dose, 25 micromoles/kg, was considered close to this level, with minor effects on body weight gain but significant effects on hematological parameters. Melphalan and J1 appeared equitoxic with no statistically significant differences. Subsequently a mouse hollow fiber model was employed with subcutaneous implantation of fibers containing human tumor cells. Three different human tumor cell lines as well as two samples of primary human tumor cells (ovarian carcinoma and chronic lymphatic leukemia) were used as tumor models. At the dose level tested there was a marked and statistically significant decrease in both T-cell leukemia CCRF-CEM and small cell lung cancer NCI-H69 tumor cell growth and viability in response to J1 as compared with both placebo and melphalan treated groups. In primary ovarian carcinoma cells only J1 treatment resulted in significant tumor regression (net cell kill). In summary the results indicate that, despite an expected short half time in the blood circulation, the promising in vitro data from the previous studies of J1 seems translatable into the in vivo situation. At equal doses of alkylating units J1, compared to melphalan, was more active in the mouse hollow-fiber model, but showed similar general toxicity.

The novel melphalan prodrug J1 inhibits neuroblastoma growthin vitroandin vivo

“…The prodrug has two hydrolysis susceptible bonds, one peptide and one ester bond. Cleaving of the peptide bond (i.e., by peptidases) leads to melphalan, and in a previous publication, we presented evidence that this cleavage results in the increased activity of J1 compared with melphalan (8).…”

“…The metalloproteinase aminopeptidase N is highly expressed in vascular endothelial cells and has been shown to play multiple roles in angiogenesis (25). Preliminary findings in our lab show that aminopeptidase N is a target of J1, 8 which may 50 Amol/kg of J1, melphalan, or no drug on days 0 and 6. Tumor growth was significantly inhibited by J1 compared with melphalan (P > 0.01).…”

“…Early weight loss comparisons favored J1 over melphalan, but differences in all other variables were not significant (significant effects on blood cell count verses control for both drugs; ref. 8). Despite being simple, elegant, and robust, the hollow fiber method suffers from some disadvantages.…”

“…Previous in vivo studies with J1 were made with the hollow fiber method in mice only (8), showing the increased potency of J1 but a similar toxicity compared with equimolar doses of melphalan. This is the first presentation of J1's activity in a xenograft model, as well as its effect in a rat model for comparison, grafts were also studied in mice (having potentially different metabolisms and different maximum tolerated doses in previous studies).…”

The novel alkylating prodrug J1: diagnosis directed activity profile ex vivo and combination analyses in vitro

“…1), exhibits significantly higher in vitro and in vivo cytotoxicity than melphalan, despite structural resemblance and identical alkylating capacity [6][7][8][9]. In vitro studies show that J1 is rapidly incorporated into the cytoplasm of tumor cell lines followed by intracellular hydrolysis, which results in release of melphalan.…”