Abstract CT054: Clinical and pharmacokinetic study with a lipidic prodrug of mitomycin-c entrapped in liposomes in metastatic colorectal cancer patients

Background: A phase 1A/1B study was conducted to investigate the safety of Promitil, a liposomal formulation of a lipidic prodrug of mitomycin-c (MLP) within an open, dose-escalating, phase (1A, n=27) followed by an expanded phase (1B, n=61) restricted to metastatic colorectal cancer (mCRC) patients after failure to two or more lines of therapy. We report here on the correlation between pharmacokinetic (PK) parameters and clinical observations in patients with mCRC. Methods: PK analysis of plasma MLP levels was obtained in 53 mCRC patients (F=26, M=27), who received Promitil every 4 weeks either as single agent (n=28), in combination with capecitabine (Cap) (n=12), or in combination with Cap and bevacizumab (Bev) (n=13). The MLP dose range was 0.5-3.5 mg/kg with most patients (N=29) receiving 2.0-2.5 mg/kg. Out of 53 patients analyzed, 39 patients completed the 3rd cycle (study week 12) and were efficacy-evaluable by CT scan and Recist criteria. PK of plasma MLP levels was analyzed by noncompartmental methods. For statistical analysis and correlations of T½ and Clearance (CL) with age, sex, BMI, baseline neutrophil/lymphocyte ratio (NLR), CEA, and survival, we used t test and Pearson or Spearman coefficients. Results: The PK of MLP was stealth-like with long T½ (~1 day), slow CL, and small Volume of distribution. Stable Disease (SD) was reported in 14 patients (36%), and Progressive Disease (PD) in 25 patients. Median survival of all 39 patients (SD+PD) was 8.3 months. SD patients had significantly longer median survival than PD patients (14.3 vs 6.5 months, p=0.0002). SD patients had significantly longer T½ and slower CL than non-SD patients. A longer T½ and slower CL were significantly correlated with longer survival. A high NLR and high CEA were correlated with shorter T½ and/or faster CL. Dose of MLP, addition of Cap and/or Bev, age and BMI did not have any apparent effect on response or survival. Conclusions: SD was indicative of extended survival. The longer circulation time of the liposomal prodrug in SD patients and its correlation with longer survival are consistent with the well-known correlation between liposome circulation time and localization in tumors. A high NLR may signal inflammatory macrophage activation resulting in shorter liposomal circulation half-life and reducing the chances of disease control. Citation Format: Alberto A. Gabizon, Esther Tahover, Ruth Perets, Talia Golan, Ravit Geva, Yasmine Amitay, Hilary Shmeeda, Patricia Ohana. Clinical and pharmacokinetic study with a lipidic prodrug of mitomycin-c entrapped in liposomes in metastatic colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT054.