JX-929, is an engineered vaccinia virus strain with increased potency optimized for cancer selectivity and the ability to activate potent chemotherapy in tumor tissue. JX-929 therefore attacks cancer both by viral attack and cancer cell lysis ("oncolysis"), plus with chemotherapy that is selectively activated in cancer tissue. Selective activation of chemotherapy in cancer tissue is designed to markedly decrease side effects and to increase potency.

To optimize tumor selectivity, two viral genes were deleted in JX-929; the goal of these deletions is to restrict replication to cells with large nucleotide pools (e.g. cancer cells) and cells with activation of the EGFR-Ras pathway, a common mutation in many cancer types. JX-929 also expresses a prodrug-activating enzyme that can convert a subsequently administered nontoxic prodrug to a cytotoxic drug. As the virus is tumor selective, production of the cytotoxic drug is concentrated at the site of the tumor, enhancing efficacy against the tumor and minimizing side effects on normal tissues.

JX-929 has been administered as a monotherapy to patients with various types of solid tumors via intratumoral & intravenous injections in a Phase 1, dose-escalation clinical trial. To date, preliminary results of this clinical trial show delivery to and replication within tumors, evidence of clinical response, and a favorable safety profile. Jennerex owns 100 percent of the worldwide rights to JX-929.