A trial of agonistic anti-CD40 antibody: Biological effects in a Cancer Research UK phase I study.

Introduction: This phase I study aimed to establish the biological effects and maximum tolerated dose (MTD) of the agonistic IgG1 chimeric anti-CD40 antibody, Chi Lob 7/4, in patients (pts) with a range of CD40 expressing solid tumors and diffuse large B-cell non-Hodgkin lymphoma (DLBL), resistant to conventional therapy. Potential mechanisms of action for agonistic anti-CD40 include direct cytotoxic effects on tumor cells, recruitment of immune effectors and conditioning of antigen-presenting cells Methodology: Chi Lob 7/4 was given by IV infusion weekly for 4 doses at a range from 0.5 to 240mg/dose. Validated ELISA's were used to quantify Chi Lob 7/4 in serum and test for anti-chimeric MAb (HACA) responses. Pharmacodynamic assessments included quantitation of T-, NK-, and B-cell numbers and activation in blood by flow cytometry, a panel of cytokines in plasma by Luminex® technology and phenotypic assessment of human plasmacytoid and myeloid dendritic cells (DC) by a novel 6 colour flow cytometry panel Planned dose escalation was in cohorts of 3 pts until MTD or biological effect, defined as reduction of peripheral blood CD19+ B-cells to 10% or less of baseline. Results: Twenty-eight pts with CD40+ tumors were treated. 11 had mesothelioma, 3 melanoma, 2 oesophageal, 2 colorectal, 2 head and neck, 2 cervical, 2 pancreatic, 2 DLBL and one each lung and thymic carcinoma. One pt with mesothelioma was re-treated with 240mg at an interval of more than 3 years, having experienced prolonged disease stabilisation after initial treatment at the 1.6mg level. Doses of up to 160mg x 4 were well-tolerated, but two pts treated with 240mg experienced grade 3 elevation of hepatic transaminase levels after 1 dose, indicating dose-limiting toxicity. The dose was reduced to 200mg x 4, and 6 pts have been treated at this level, with 1 experiencing grade 3 elevation of liver enzymes after 2 doses but 5 completing 4 doses without difficulties. Infusion reactions occurred at 16mg doses, largely preventable by corticosteroid premedication. Chi Lob 7/4 levels were measurable at doses of 50mg and above. At 200mg, Cmax on day 1 was 47-60mcg/ml, with terminal half life > 7 days and levels > 30 mcg/ml detectable at 1 week. HACA responses were common at low doses (5-50mg) but absent at higher doses (160-240mg), coincident with dose-dependent partial depletion of peripheral blood CD19+ B-cells. Transient falls in blood NK-cells occurred after the first dose of Chi Lob 7/4 at 16mg or greater, with elevated MIP-1beta maximal at 3-6 hours. Dose-dependent elevations in IL-12 occurred above 160mg, rising throughout the period of treatment. Activation of NK cells and monocytes was detected by elevated CD54 expression at doses of 160mg or above, but there was no consistent change in T-cell markers. Response assessment at week 8 showed stable disease after 15 courses, and progression after 14. The median duration of disease stabilization was 6 months, maximum 37. The pt re-treated for progressive mesothelioma after 3 years remains with stable disease at 17 months after a single 240mg dose. Conclusion: This antibody elicits B-cell depletion, and there was evidence of consistent NK and macrophage activation. The dose-limiting toxicity was liver enzyme rise, with the MTD being 200mg/dose (range between 2.1 - 3.3 mg/kg based on patient body weight). Disease stabilization in some cases suggests that further testing is indicated in CD40-expressing malignancies.