Preclinical Safety Evaluation in Rats of a Polymeric Matrix Containing an siRNA Drug Used as a Local and Prolonged Delivery System for Pancreatic Cancer Therapy.

Conventional chemotherapy treatments for pancreatic cancer are mainly palliative. RNA interference (RNAi)-based drugs present the potential for a new targeted treatment. LOcal Drug EluteR (LODER(TM)) is a novel biodegradable polymeric matrix that shields drugs against enzymatic degradation and releases small interfering RNA (siRNA) against G12D-mutated KRAS (siG12D). siG12D-LODER has successfully passed a phase 1/2a clinical trial. Such a formulation necessitates biocompatibility and safety studies. We describe the safety and toxicity studies with siG12D-LODER in 192 Hsd:Sprague Dawley rats, after repeated subcutaneous administrations (days 1, 14, and 28). Animals were sacrificed on days 29 and 42 (recovery phase). In all groups, no adverse effects were noted, and all animals showed favorable local and systemic tolerability. Histopathologically, LODER implantation resulted in the expected capsule formation, composed of a thin fibrotic tissue. On the interface between the cavity and the capsule, a single layer composed of macrophages and multinucleated giant cells was observed. No difference was noted between the placebo and siG12D-LODER groups. These findings provide valuable information for future preclinical studies with siRNA-bearing biodegradable polymers and for the safety aspects of RNAi-based drugs as a targeted therapy.

Multistep, effective drug distribution within solid tumors.

The distribution of drugs within solid tumors presents a long-standing barrier for efficient cancer therapies. Tumors are highly resistant to diffusion, and the lack of blood and lymphatic flows suppresses convection. Prolonged, continuous intratumoral drug delivery from a miniature drug source offers an alternative to both systemic delivery and intratumoral injection. Presented here is a model of drug distribution from such a source, in a multistep process. At delivery onset the drug mainly affects the closest surroundings. Such 'priming' enables drug penetration to successive cell layers. Tumor 'void volume' (volume not occupied by cells) increases, facilitating lymphatic perfusion. The drug is then transported by hydraulic convection downstream along interstitial fluid pressure (IFP) gradients, away from the tumor core. After a week tumor cell death occurs throughout the entire tumor and IFP gradients are flattened. Then, the drug is transported mainly by 'mixing', powered by physiological bulk body movements. Steady state is achieved and the drug covers the entire tumor over several months. Supporting measurements are provided from the LODER system, releasing siRNA against mutated KRAS over months in pancreatic cancer in-vivo models. LODER was also successfully employed in a recent Phase 1/2 clinical trial with pancreatic cancer patients.

RNAi therapy targeting KRAS in combination with chemotherapy for locally advanced pancreatic cancer patients.

PURPOSE: The miniature biodegradable implant siG12D-LODER™ was inserted into a tumor and released a siRNA drug against KRAS(G12D) along four months. This novel siRNA based drug was studied, in combination with chemotherapy, as targeted therapy for Locally Advanced Pancreatic Cancer (LAPC). METHODS: An open-label Phase 1/2a study in the first-line setting of patients with non-operable LAPC was initiated. In this study patients were assigned to receive a single dose of siG12D-LODERs, in three escalating dose cohorts (0.025mg, 0.75mg and 3.0mg). Gemcitabine was given on a weekly basis, following the siG12D-LODERTM insertion, until disease progression. The recommended dose was further examined with modified FOLFIRINOX. The follow up period was eight weeks and survival until death. RESULTS: Fifteen patients with LAPC were enrolled. Among the 15 treated patients, the most frequent adverse events observed were grade 1or 2 in severity (89%); five patients experienced serious adverse events (SAEs). In 12 patients analyzed by CT scans, none showed tumor progression, the majority (10/12) demonstrated stable disease and two showed partial response. Decrease in tumor marker CA19-9 was observed in 70% (7/10) of patients. Median overall survival was 15.12 months; 18 month survival was 38.5%. CONCLUSIONS: The combination of siG12D-LODER™ and chemotherapy is well tolerated, safe and demonstrated a potential efficacy in patients with LAPC. NCT01188785.