PG-545

Acute pancreatitis (AP) is a common gastrointestinal disease with high morbidity and mortality rate. Unfortunately, neither the etiology nor the pathophysiology of AP are fully understood and causal treatment options are not available. Recently we demonstrated that heparanase (Hpa) is adversely involved in the pathogenesis of AP and inhibition of this enzyme ameliorates the manifestation of the disease. Moreover, a pioneer study demonstrated that Aspirin has partial inhibitory effect on Hpa. Another compound, which possesses a mild pancreato‐protective effect against AP, is Trehalose, a common disaccharide. We hypothesized that combination of Aspirin, Trehalose, PG545 (Pixatimod) and SST0001 (Roneparstat), specific inhibitors of Hpa, may exert pancreato‐protective effect better than each drug alone. Thus, the current study examines the pancreato‐protective effects of Aspirin, Trehalose, PG545 and SST0001 in experimental model of AP induced by cerulein in wild‐type (WT) and Hpa over‐expressing (Hpa‐Tg) mice. Cerulein‐induced AP in WT mice was associated with significant rises in the serum levels of lipase (X4) and amylase (X3) with enhancement of pancreatic edema index, inflammatory response, and autophagy. Responses to cerulein were all more profound in Hpa‐Tg mice versus WT mice, evident by X7 and X5 folds increase in lipase and amylase levels, respectively. Treatment with Aspirin or Trehalose alone and even more so in combination with PG545 or SST0001 were highly effective, restoring the serum level of lipase back to the basal level. Importantly, a novel newly synthesized compound termed Aspirlose effectively ameliorated the pathogenesis of AP as a single agent. Collectively, the results strongly indicate that targeting Hpa by using anti‐Hpa drug combinations constitute a novel therapy for this common orphan disease.

PG545 (Pixatimod) is a highly sulfated small molecule known for its ability to inhibit heparanase and disrupt signaling mediated by heparan-binding-growth factors (HB-GF). Previous studies indicated that PG545 inhibits growth factor-mediated signaling in ovarian cancer (OC) to enhance response to chemotherapy. Here we investigated the previously unidentified mechanisms by which PG545 induces DNA damage in OC cells and found that PG545 induces DNA single- and double-strand breaks, reduces RAD51 expression in an autophagy-dependent manner and inhibits homologous recombination repair (HRR). These changes accompanied the ability of PG545 to inhibit endocytosis of the heparan-sulfate proteoglycan interacting DNA repair protein, DEK, leading to DEK sequestration in the tumor microenvironment (TME) and loss of nuclear DEK needed for HRR. As a result, PG545 synergized with poly (ADP-ribose) polymerase inhibitors (PARPis) in OC cell lines in vitro and in 55% of primary cultures of patient-derived ascites samples ex vivo. Moreover, PG545/PARPi synergy was observed in OC cells exhibiting either de novo or acquired resistance to PARPi monotherapy. PG545 in combination with rucaparib also generated increased DNA damage, increased antitumor effects and increased survival of mice bearing HRR proficient OVCAR5 xenografts compared to monotherapy treatment in vivo. Synergistic antitumor activity of the PG545/rucaparib combination was likewise observed in an immunocompetent syngeneic ID8F3 OC model. Collectively, these results suggest that targeting DEK-HSPG interactions in the TME through the use of PG545 may be a novel method of inhibiting DNA repair and sensitizing cells to PARPis.