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Several routes and methods of DNA immunization have been shown to generate Ab, Th cells, and CTL responses. However, few studies have directly compared the immune responses generated by different routes and methods of DNA immunization. Utilizing an influenza hemagglutinin (H1)-expressing plasmid, we compared the immune response produced by saline injection of DNA into skin or muscle, and gene gun immunization of skin or muscle. We found that saline-DNA immunization raised a predominantly Th1 response with mostly IgG2a anti-H1 Ab, while gene gun DNA immunization produced a predominantly Th2 response with mostly IgG1 anti-H1 Abs. These distinct types of immune responses were generated by the method, not the route, of DNA immunization. The initial immunization established the Th cell-type of the immune response. The Th cell-type did not change with further DNA immunizations by the same or the alternate method, or after a viral challenge. The ability to generate different Th types was not due to differences in the doses of DNA used in saline and gene gun DNA immunization. These findings have important implications for vaccine design and studies of the mechanism of Th cell differentiation.

331 Background: Programmed death-1 (PD-1), a T-cell inhibitory receptor, may suppress antitumor immunity. BMS-936558, a fully human PD-1 blocking antibody, has shown antitumor activity and manageable toxicity after biweekly dosing (Sznol, ASCO 2010, #2506). This report provides an update on safety and antitumor activity with special emphasis on RCC. Methods: An open-label phase I dose escalation study of BMS-936558 was conducted in patients (pts) with treatment refractory metastatic clear-cell renal cell carcinoma (RCC), castrate-resistant prostate cancer (CRPC), melanoma (MEL), non-small cell lung cancer, or colorectal cancer (CRC). Dose escalation continued to 10 mg/kg when an expansion cohort for pts (16) with each tumor type was opened for additional safety and efficacy information. Tumor response (RECIST) was evaluated every 8 weeks. Clinically stable pts with early PD could continue until further PD or clinical deterioration. Results: 126 pts (18 RCC) were treated with 1, 3, or 10 mg/kg. MTD was not reached. Across all doses, the most common AEs (Any/grade 3-4) were fatigue (45.2%/6.3%) and diarrhea (30.2%/0.8%) while the most common drug-related AEs (Any/grade 3-4) were fatigue (20.6%/0.8%), rash (11.9%/0%), pruritus (11.3%/0%), and diarrhea (10.3%/0.8%). There was no apparent relationship between dose and frequency of AEs. One pt died with sepsis while being treated for drug-related grade 4 pneumonitis. The median number of prior treatment regimens in the RCC cohort was 2 (range 1-6). Of the 18 RCC pts, 16 were treated with 10 mg/kg. The median duration of treatment was 7.6+mo. ORR was 5/16 (31.2%) and SD>4mo was 6/16 (37.5%). The median duration of response was 4.0+ mo (3.7-7.4+ mo). Of the 2 RCC pts treated with 1 mg/kg, 1 obtained a CR (12+ mo) and 1 had SD (21+ mo). For evaluable CRPC pts, 1/15 pts (6.7%) obtained a PR (2+ mo) and 3/15 (20%) had SD>4mo. Conclusions: BMS-936558 administered biweekly is tolerable and has encouraging antitumor activity in a previously treated patients with RCC. Data on baseline characteristics, long-term toxicity and response duration will be updated at the meeting. [Table: see text]

3007 Background: CD137 is a member of the TNFR family and functions as a costimulatory molecule. In preclinical studies BMS- 663513, a fully human anti-CD137 agonist monoclonal antibody provided costimulation to CD8+ and CD4+ T-cells, leading to enhanced IFNγ production, cytolytic activity, and increased survival. We conducted a first-in-human phase I dose-escalation study of BMS-663513 in pts with CA. Methods: BMS-663513 was administered IV every 3 weeks. In Part 1, the dose was escalated (0.3, 1, 3, 6, 10, and 15 mg/kg) in cohorts of 3–6 pts. In Part 2, pts with melanoma, RCC, and ovarian CA, 30 per CA, were stratified by tumor type and randomized to receive 1, 3, and 10 mg/kg dose levels. Tumor response (modified WHO) was determined after the 4th dose and then every 2 doses. After 4 doses, treatment continued in pts with antitumor activity and without dose-limiting toxicity (DLT). Tumor biopsies were obtained from pts in Part 1 pretreatment and during cycle 2; PBMC, serum, and plasma were also obtained...