Objective  To assess whether a new heat‐killed Mycobacterium vaccae preparation (SRL172), which enhances cell‐mediated immunity and has been proposed for use as an immunotherapeutic agent against cancer, is safe in patients with advanced hormone‐refractory prostate cancer, can stimulate desirable cytokine changes in these patients and modulate the progression of the disease. Patients and methods  Ten patients were given SRL172 intradermally at regular intervals. The serum prostate specific antigen (PSA) level was used as a surrogate marker of response. The proportion of peripheral blood mononuclear cells (PBMC) secreting interleukin 2 (IL2), interferon gamma (IFNγ) and interleukin 4 (IL4) was measured by flow cytometry (FACS) before and after vaccination to assess whether the treatment induced a Th2 (predominantly humoral) to Th1 (predominantly cell‐mediated) switch. Results  There were no significant adverse events. In five patients the serum PSA declined during the trial and in two of these there was no concomitant change of therapy apart from vaccination with SRL172. Before vaccination with SRL172 patients had a low proportion of PBMC producing IFNγ and IL2 (all 10) and a higher proportion secreting IL4 (all three tested), suggesting a predominantly Th2 cytokine profile. After vaccination the proportion of IL4 secreting PBMC fell in all three patients tested. The proportion of IL2 secreting PBMC increased in three patients whose PSA fell. The proportion of IFNγ‐secreting cells remained depressed in nine of 10 patients. Conclusion  Two patients with advanced hormone‐refractory prostate cancer had a PSA response to the vaccination with SRL172. The proportion of PBMC secreting IL2 is a potential marker of response to immunotherapy.

Objective To evaluate the potential of heat-killed Results SRL172 was eCective as an adjuvant to autologous whole tumour cell vaccination in the prevention Mycobacterium vaccae (SRL172) as a nonspecific immunostimulant and as an adjuvant to whole tumour cell of MAT-LyLu tumours and the survival benefit was equivalent to that provided when the adjuvant was vaccination in the rat model of prostate cancer. Materials and methods SRL172 was used as a vaccine live-attenuated BCG. SRL172 alone did not reduce tumour take or tumour growth in this model and in the prevention and treatment of subcutaneous tumours in rats. Prevention experiments were conduc-neither strategy was eCective in delaying the growth of established MAT-LyLu tumours. In the Lobund-ted using subcutaneous MAT-LyLu tumours in Copenhagen rats, comparing vaccination with Wistar rat vaccination with autologous whole tumour cells and SRL172 significantly delayed the growth of SRL172 alone, SRL172 plus autologous cells, and bacille Calmette-Guèrin (BCG) plus autologous cells established tumours. Conclusion Mycobacterium vaccae deserves further evalu-before tumour implantation. Treatment experiments were conducted using subcutaneous MAT-LyLu ation as an adjuvant to whole tumour cell vaccination in a phase I clinical trial in patients with prostate tumours in the Copenhagen rat and subcutaneous PAIII tumours in the Lobund-Wistar rat. Tumours cancer. Keywords Prostate cancer, immunotherapy, Myco-were induced by subcutaneous injection with tumour cells. Animals were then vaccinated with autologous bacterium vaccae, vaccine, rat model cells, autologous cells plus SRL172, or SRL172 alone. or by the co-injection of adjuvant [5]. In animal models

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