A phase I, dose escalation, single dose trial of oral attenuated salmonella typhimurium containing human IL-2 in patients with metastatic gastrointestinal cancers

Salmonella has been shown to preferentially colonize solid tumors. It is known that toxicity limits the systemic administration of immunomodulatory cytokines that have a significant anticancer effect. Therefore, we tested a unique cancer treatment strategy comprised of oral delivery of Saltikva, an attenuated strain of Salmonella typhimurium that contain the human gene for interleukin-2. In preclinical experimentation, a significant antitumor effect without toxicity was observed. A dose escalation, single dose, Phase I trial was conducted. Dose escalation (105 to 1010) while monitoring for dose limiting toxicity and response was performed. Flow cytometry was conducted to determine the immunologic effect. In total 22 patients were administered Saltikva. Eight patients did not complete the trial. No toxicity or adverse events were observed. There was no survival advantage. Flow cytometry demonstrated an increase in circulating natural killer (NK) cells and NK-T cells when comparing the prestudy period. The results of this phase I dose escalation study show that oral attenuated S. typhimurium containing the human interleukin-2 gene caused no significant toxicities up to doses of 1010 colony forming unit. There was no evidence of partial or complete response. All patients had progressive disease and eventually succumbed to their illness. Although no survival advantage was seen in this single dose study, the statistically significant increase in circulating NK and NK-T cell demonstrates an immunologic effect from this treatment regimen and suggest that a multiple dose study should be undertaken.