3054 Background: TALL-104 is an irradiated human leukemic T cell line (CD3+, CD4- CD8+, CD56+, CD16-) grown in IL-2- containing medium, that has the ability to kill tumor cells in preclinical models in a MHC unrestricted way. A phase I trial in metastatic breast cancer patients, has shown that multiple i.v. infusions (infs) of TALL-104 cells can be given safely. In order to optimise the tumor:effector cell ratio, we have designed a phase I study of intraperitoneal infs of γ-irradiated TALL-104 cells. Methods: Patients (pts) with peritoneal carcinosis from ovarian or gastrointestinal tumors not responding to at least 2 lines of chemotherapy were eligible for study entry. The treatment included 5 i.p. infs (day 1, 3, 5, 15, 30) and the study aimed to test three cell dose levels: 1 x 108, 5 x 108, 2.5 x 109. End points of the study were: safety, kinetic of TALL-104 cells on ascites (if present) and peripheral blood (PB) by PCR, levels of cytokines (TGF-β, GM-CSF, IL-2, IL-4, IL-10, IFN-γ, TNF-a and -β, HGF, sIL-2R, sICAM-1) on ascites and serum, and cytotoxicity of autologous PB mononuclear cells (MNC) against K562 cells. Results: So far 10 pts have been treated: 6 with GI and 4 with ovarian cancer; 7 patients had ascites. Five pts have been treated at the 1st and 5 pts at the 2nd dose level. No treatment-related adverse events were observed. TALL-104 cells were detected in ascites (100 % of the pts) and PB (43 % of the pts) up to 48 hrs after the infs. Cytotoxicity of MNC showed a mean 5-fold increase at day 3 through 7 and it was still evident at day 30 in both dose levels. Cytokine levels are available for the first 5 pts. In one pt 18-fold increase of TNF-a was observed in ascites after the first infusion with a peak of 40-fold at day 15. sIL-2R and sICAM-1 showed both a mean 1.2-fold and 1.5-fold increase in serum in ascites respectively up to day 45. TGF-β1 level increased in average 3.3-fold in serum and 1.5-fold in ascites during the same observation period. HGF showed a mean 1.2-fold increase both in serum and ascites. Conclusions: These preliminary results show that the i.p. infusion of TALL-104 is safe. Moreover, the increased autologous cell-mediated cytotoxicity and the levels of soluble cytokines after i.p. infs indicate that TALL-104 cells may elicit potential antitumor activity. No significant financial relationships to disclose.