Intratumoral delivery of pmIL12, an interleukin-12 encoding plasmid, via gene electrotransfer (GET) has shown promising preclinical results, paving the way for a Phase I clinical study. The research, published in Scientific Reports, details the non-clinical evaluation of pmIL12 gene therapy, assessing its pharmacodynamics, pharmacokinetics, and systemic toxicology in a murine model.
The study utilized BALB/cAnNCrl mice with induced CT26 tumors, randomized into groups receiving varying doses of pmIL12 via GET. The high dose (2 mg/ml) represented the maximum feasible dose (MFD), with lower doses at 1 mg/ml and 0.5 mg/ml. Researchers evaluated tumor growth, transgene expression, immune cell infiltration, plasmid biodistribution, and potential toxic effects.
Anti-Tumor Effectiveness and Immune Response
Pharmacodynamic evaluations confirmed the anti-tumor effectiveness of pmIL12 GET. Tumor diameters were measured three times per week, and tumor volume was calculated. The mice were euthanized when the tumor volume reached 1000 mm3. The degree of immune cell infiltration (granulocytes and lymphocytes) was assessed by two independent pathologists blinded to the experimental groups. The degree of infiltration was scored on a scale from 0 to 3, with 0 indicating no infiltration and 3 indicating strong infiltration.
Biodistribution and Persistence
Pharmacokinetic studies tracked the biodistribution and persistence of the pmIL12 plasmid in various organs, including the skin around the tumor, liver, gonads, heart, spleen, kidney, brain, lymph nodes, eyes, and lungs. Quantitative real-time PCR (qRT-PCR) was used to quantify the number of plasmid DNA (pmIL12) copies present in various organs after pmIL12 GET into CT26 tumors. The collection points were 2, 8 and 14 days after pmIL12 GET into CT26 tumors.
Safety Profile
Systemic toxicology was assessed through monitoring of mouse weight, behavior using the mouse grimace scale, and general health. Full necropsies and histopathological evaluations of organs were performed. Blood samples were analyzed for complete blood count (CBC), white blood cell differential count (DIFF), biochemical parameters (BC) and IgG and IgM titers.
The results indicated that pmIL12 GET was well-tolerated, with no significant systemic toxicity observed at the tested doses. These findings support the approval of a Phase I clinical study to evaluate the safety and efficacy of pmIL12 gene therapy in humans.
