Delivery of a liposomal c-raf-1 antisense oligonucleotide by weekly bolus dosing in patients with advanced solid tumors: A phase I study

Purpose: Rapid cleavage in vivo and inefficient cellular uptake limit the clinical utility of antisense oligonucleotides (AON). Liposomal formulation may promote better intratumoral AON delivery and inhibit degradation in vivo . We conducted the first clinical evaluation of this concept using a liposomal AON complementary to the c-raf-1 proto-oncogene (LErafAON). Experimental Design: A dose escalation study was done to determine the maximum tolerated dose and to characterize the toxicities of LErafAON given as weekly intravenous infusion for 8 weeks to adults with advanced solid tumors. Pharmacokinetic analysis and evaluation of c-raf-1 target suppression in peripheral blood mononuclear cells were included. Results: Twenty-two patients received LErafAON (median 7 infusions; range 1–27) at doses of 1, 2, 4, and 6 mg/kg/week. Across all dose cohorts patients experienced infusion-related hypersensitivity reactions including flushing, dyspnea, hypoxia, rigors, back pain, and hypotension. Prolonged infusion duration and pretreatment with acetaminophen, H1- and H2-antagonists, and corticosteroids reduced the frequency and severity of these reactions. Progressive thrombocytopenia was dose-limiting at 6 mg/kg/week. No objective responses were observed. Two patients treated at the maximum tolerated dose of 4 mg/kg/week had evidence of stable disease, with dosing extended beyond 8 weeks. Pharmacokinetic analysis revealed persistence of detectable circulating rafAON at 24 hours in 7 of 10 patients in the highest 2 dose cohorts. Suppression of c-raf-1 mRNA was noted in two of five patients analyzed. Conclusions: Dose-independent hypersensitivity reactions and dose-dependent thrombocytopenia limited tolerance of LErafAON. Future clinical evaluation of this approach will depend on modification of the liposome composition.