PNU-214565, a SAg-based tumor targeted therapy, is safe when given as a single 3-hour infusion at doses up to 1.5 ng/kg. The MTD for a single dose was not determined. The safety of a repeated dose schedule is currently under investigation, beginning with doses determined to be safe in this trial.

The bispecific monoclonal antibody (bsmAb) 2B1, targeting the extracellular domain of c-erbB-2, the protein product of the HER-2/neu proto-ocogene, and Fc gamma RIII (CD16), expressed by human natural killer cells, neutrophils and differentiated monocytes, mediates the specific cytotoxic activity of these effector cells to tumor cells. A group of 24 patients with c-erbB-2-overexpressing tumors were treated with intravenously administered 2B1 in a phase I clinical trial and followed after treatment to evaluate the diversity and extent of the 2B1-induced humoral immune responses. As expected, 17 of 24 patients developed human anti-(murine Ig) antibodies (HAMA) to whole 2B1 IgG in a range from 100 ng/ml to more than 50000 ng/ml; 10 of these patients (42%) had strong (at least 1000 ng/ml) HAMA responses, some of which were still detectable at day 191. These responses were usually associated with similar reactivity to the F(ab')2 fragments of the parental antibodies 520C9 (anti-c-erbB-2) and 3G8 (anti-CD16). We sought evidence of an idiotypic cascade induction, indicating a prolonged specific treatment-induced effect on at least one selected target of 2B1. Using competition-based enzyme-linked immunosorbent assays, specific anti-idiotypic antibodies (Ab2) were detectable against 520C9 in 11 patients and against 3G8 in 13 patients. Peak anti-idiotypic antibodies generally occurred 3-5 weeks from treatment initiation, with a downward trend thereafter. There was a statistically significant correlation among the induction of significant HAMA responses, anti-idiotypic antibody production and the development of antibodies to c-erbB-2. The anti-c-erbB-2 responses, which were distinct from anti-anti-idiotypic (Ab3) antibodies, were detected in the post-treatment sera of 6/16 patients examined. No obvious correlation could be made between the development of humoral immune responses, the dose received, and the clinical response. Future investigation involving 2B1 therapy will concentrate on investigating an association of these humoral responses to any c-erbB-2-specific cellular responses. Manipulations of 2B1 therapy effects that augment immunity to c-erbB-2 could provide additional avenues for immunotherapy with this and other bispecific antibodies.

3506 Background: This multicenter, randomized study assessed efficacy & safety for 3 irinotecan/fluoropyrimidines combinations in previously untreated mCRC. In a 3 × 2 factorial design, we also assessed whether celecoxib added to chemotherapy (CT) improved CT efficacy and/or reduced toxicity. Methods: Pts were randomized to: FOLFIRI - irinotecan (I) 180 mg/m2, leucovorin (LV) 400 mg/m2, 5-FU bolus 400 mg/m2, & infusional 5-FU 2400 mg/m2 over 46 hours q 2 wks; modified IFL (m-IFL) - I 125 mg/m2, LV 20 mg/m2, & bolus 5-FU 500 mg/m2 wkly × 2, q 3 wks; or CapeIri - I 250 mg/m2 day 1 & capecitabine 1000 mg/m2 po BID × 14 days, q 3 wks. Pts were also randomized to concurrent celecoxib (400 mg po BID) or placebo in a double-blind fashion. Time to progression (TTP) was the primary endpoint. Results: 430 pts were enrolled from 2/03 to 4/04, prior to an amendment that added bevacizumab to CT arms. Baseline characteristics were balanced. TTP for FOLFIRI (median = 8.2 mos) was significantly better than for either m-IFL (6.0 mos; p = 0.01) or CapeIri (5.7 mos; p = 0.01). Overall survival (OS) also favored FOLFIRI (median = 23.1 mos) compared to either m-IFL (17.6 mos; p=0.10) or CapeIri (18.8 mos; p = 0.19). Common grade ≥ 3 toxicities are listed below. CapeIri had the highest rates of nausea, vomiting, diarrhea, dehydration & hand-foot syndrome, whereas FOLFIRI had lower rates. Among all 430 pts, median TTP did not differ for pts randomized to celecoxib compared to placebo (6.9 vs 6.9 mos; p=0.71). Median OS was also similar for celecoxib vs placebo (19.5 vs 18.8 mos; p=0.63). CT toxicities did not differ for celecoxib vs placebo. Rates for MI/stroke were 1.5% for celecoxib and 1.9% for placebo. Conclusions: First-line FOLFIRI offers a superior TTP when compared to m-IFL or CapeIri; OS & toxicity analyses also favored FOLFIRI. Celecoxib neither improved CT efficacy nor reduced CT toxicity. Updated survival data & data on pts enrolled after the addition of bevacuzimab will be presented. [Table: see text] [Table: see text]