Two studies were carried out to evaluate heat-killed Mycobacterium vaccae
SRL172 as an immunotherapeutic agent for patients with metastatic, post-
nephrectomy,
renal cell carcinoma. In the first study, 60 patients in France and the UK received
injections of
SRL172, and their survival was compared with that of historical controls who had been treated either with
biological response modifiers (IL-2, IFN-alpha) or
chemotherapy. In the second study, 36 patients were randomised to receive treatment with
IL-2 alone or
IL-2 plus
SRL172. Survival and adverse events related to the treatments were assessed and compared between treatment groups. The first study showed that those treated with
SRL172 alone survived equally as long as those receiving
IL-2 or IFN-alpha and both treatment groups survived longer than those on
chemotherapy (p<0.001), a result supported by Cox's proportional hazards regression analysis. The second study, stopped early due to
drug supply issues, showed that the addition of
SRL172 to
IL-2 made no difference to survival compared to
IL-2 alone, in the limited numbers treated. Adverse events occurring in those receiving
SRL172 in the first study were mild and in the second study those receiving
IL-2 alone had significantly more adverse events than those receiving
SRL172 plus
IL-2 (p<0.001). It is concluded that
SRL172 may have activity in metastatic
renal cancer and has very low toxicity, making it worthy of further study.