Combining Sorafenib with the antivascular action of microbubbles for the treatment of hepatocellular carcinoma

In this study we investigate the feasibility of enhancing the ability of Sorafenib to treat hepatocellular carcinoma (HCC) by coupling it with ‘antivascular’ ultrasound stimulated microbubble (USMB) exposures. These are exposure levels that we have previously reported to produce rapid acute vascular shutdown in preclinical tumor models. Experiments were conducted using Heb3B HCC tumors initiated subcutaneously in the legs of mice. USMB treatments were conducted at 1 MHz employing short bursts (0.00024 duty cycle) at 1.4 MPa combined with an experimental lipid encapsulated agent. Longitudinal experiments were conducted with control (CN), drug only (SF), USMB-only, and combined USMB+drug (USMB-SF) groups (n=6–8/group). In drug groups, animals received Sorafenib at 30mg/kg through daily oral gavage. USMB treatments were performed for 2 consecutive weeks, starting two days after drug treatments began. Acute experiments were also conducted where animals were sacrificed after the injection of a perfusion stain (DiOC7) at 2 or 24 hours post-treatment with tissue excised for analysis. USMB treatments induced an acute reduction of tumor blood flow as confirmed with US contrast imaging and perfusion staining. Longitudinal experiments demonstrated both the USMB and SF groups had non-significant trends of reduced sizes relative to the CN group for time points >=11 days. The USMB-SF group was significantly smaller than the CN group for days >=11 (p<0.01) and for the SF group at days >=14 (p<0.01 to p<0.02). The growth delay (time to reach 5x initial size) for the combined group was 9.4, 8.3 and 8.5 days longer than CN, SF and USMB groups respectively. These results indicate the preclinical feasibility of potentiating Sorafenib with antivascular USMB effects to treat HCC tumors. Notably, this approach employs exposure levels that are low relative to ablative treatments which would facilitate the exposure of larger tumor volumes.