Strain specific analysis of OX40 mRNA expression in wild-type C57BL/6JNifdc mice and homozygous B-hOX40 mice by RT-PCR. Spleen RNA was isolated from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hOX40 mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human OX40 primers. Mouse OX40 mRNA was only detectable in wild-type mice Human OX40 mRNA was exclusively detectable in homozygous B-hOX40 mice but not in wild-type mice.

Strain specific OX40 expression analysis in homozygous B-hOX40 mice by flow cytometry. Splenocytes were collected from WT and homozygous B-hOX40 (H/H) mice stimulated with anti-CD3ε in vivo (7.5 μg/mice), and analyzed by flow cytometry with species-specific anti-OX40 antibody. Mouse OX40 was exclusively detected in WT mice. Human OX40 was exclusively detected in homozygous B-hOX40 but not WT mice.

Antitumor activity of anti-human OX40 antibody in B-hOX40 mice. (A) Anti-human OX40 antibody inhibited MC38 tumor growth in B-hOX40 mice. Murine colon cancer MC38 cells (5ⅹ10⁵) were subcutaneously implanted into homozygous B-hOX40 mice (male, 4-6 week-old, n=5). Mice were grouped when tumor volume reached approximately 100 mm³, at which time they were treated with anti-human OX40 antibody and schedules indicated in panel (B) Body weight changes during treatment. As shown in panel A, anti-human OX40 antibody was efficacious in controlling tumor growth in B-hOX40 mice, demonstrating that the B-hOX40 mice provide a powerful preclinical model for in vivo evaluation of anti-human OX40 antibodies. Values are expressed as mean ± SEM

Antitumor activity of anti-human OX40 antibody in B-hOX40 mice. (A) Anti-human OX40 antibody inhibited MC38 tumor growth in B-hOX40 mice. Murine colon cancer MC38 cells (5ⅹ10⁵) were subcutaneously implanted into homozygous B-hOX40 mice (female, 4-6 week-old, n=6). Mice were grouped when tumor volume reached approximately 150±50 mm³, at which time they were treated with anti-human OX40 antibody with different doses and schedules indicated in panel (B) Body weight changes during treatment. As shown in panel A, anti-human OX40 antibody MOXR0916(in house) was efficacious in controlling tumor growth in B-hOX40 mice, demonstrating that the B-hOX40 mice provide a powerful preclinical model for in vivo evaluation of anti-human OX40 antibodies. Values are expressed as mean ± SEM