Polymeric rapamycin nanoparticles encapsulating ponatinib cause regression of venous malformations in mice

Venous malformations (VMs) are caused by activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) and Abelson murine leukemia viral oncogene homolog 1 (c-ABL) pathways. Daily oral administration of rapamycin (RAPA), an mTOR pathway inhibitor, has limited effectiveness in promoting lesion regression in patients with TEK receptor tyrosine kinase (TIE2)–mutated VMs. This may be due to poor bioavailability, frequent dosing requirements, and off-target effects that make maintaining adherence difficult. Recent preclinical studies have shown that combination treatment with RAPA and a c-ABL inhibitor [ponatinib (PON)] resulted in regression of VMs in a murine model; however, daily oral dosing was required. Here, we describe the formulation of polymeric RAPA, which acts as both a polymeric drug and a drug delivery carrier. The polymer was synthesized by polymerization of methacryloylated RAPA and terminated with polyethylene glycol (PEG-pRAPA). PEG-pRAPA self-assembled to form 30-nanometer nanoparticles (PEG-pRAPA NPs) and enabled the encapsulation of PON (PEG-pRAPA@PON NPs). PEG-pRAPA@PON NPs provided sustained release of both PON and PEG-pRAPA in vitro, reducing AKT phosphorylation comparably to free RAPA and PON. In a murine model of VMs, a single intravenous dose of PEG-pRAPA@PON NPs caused 70% VM regression over 20 days and a 6.3-fold reduction in CD31-positive (human-derived) blood vessels. There was no evidence of systemic toxicity or organ dysfunction after treatment. These findings demonstrated that PEG-pRAPA is an effective polymeric drug and drug delivery platform and support the hypothesis that nanoparticle-based pharmacotherapy can be an effective treatment strategy for VMs.