SGN-40 (Anti-huCD40 mAb) Monotherapy Induces Durable Objective Responses in Patients with Relapsed Aggressive Non-Hodgkin’s Lymphoma: Evidence of Antitumor Activity from a Phase I Study.

CD40 is a member of the TNF receptor family and is widely expressed on B-cell malignancies. SGN-40 is a humanized antibody against CD40 with effector cell function and partial agonistic activity. Based on potent in vitro and in vivo preclinical activity, a multi-institutional, multi-dose phase I study was conducted to test the safety, pharmacokinetic properties, immunogenicity, and antitumor activity of intravenous SGN-40 in patients with relapsed NHL. Patients with multiple histologic subtypes of NHL were enrolled on this study, including diffuse large B-cell (DLBCL; 14), follicular (FCL; 9), mantle cell (MCL; 9), marginal zone (MZL; 2) and small lymphocytic (SLL; 1). After dose-dependent inflammatory symptoms were identified following the first infusion of SGN-40 in a separate phase I study (i.e. cytokine release syndrome, including headache, fever, muscle aches), this study was modified such that patients were treated with a dose-loading schedule: 1 mg/kg of SGN-40 on day 1 and day 4 and subsequent intra-patient dose-escalation during weeks 2–5 to a maximum dose of 3, 4, 6, or 8 mg/kg over four cohorts. Subsequently, a rapid dose-loading schedule was tested in one cohort (40% increase in total SGN-40 administered during cycle 1). Responding patients or those with stable disease were eligible for a second cycle, consisting of four consecutive weekly infusions at the cohort-specific maximum dose of SGN-40. Most adverse events were grade 1 or 2 and included fatigue (31%), headache (26%), chills (17%), pyrexia (17%), elevated hepatic transaminases (11%), and hypotension (11%). Transient drug-related grade 3 adverse events included conjunctivitis and unilateral loss of visual acuity, anemia, and elevated hepatic transaminases, each in a single patient. There was no difference in the incidence or severity of adverse events at higher doses of SGN-40 nor was there a difference in the safety profiles of the gradual vs. rapid dose-loading schedules. Ten of 35 enrolled patients received a second cycle of treatment without any evidence of cumulative toxicity. No immune responses against SGN-40 have been detected among 16 NHL patients tested to date. Preliminary pharmacokinetic parameters are similar to those seen in preclinical toxicity studies. Durable objective responses have been observed in heavily pre-treated patients. Eight patients with DLBCL completed cycle 1 and received a maximum dose of at least 3 mg/kg SGN-40 with an objective response rate of 37.5% (i.e. 1 CR and 2 PR) and 2 SD. Additional objective responses were seen in one patient with MCL (CR) and one patient with MZL (PR). The median duration of response for these 5 patients has not yet been reached (range 8–37 weeks). Analyses are ongoing to evaluate the role of CD40 expression levels and the relationship of FcγR polymorphisms to response. In conclusion, SGN-40 has favorable safety data and encouraging antitumor activity. A phase II study of single-agent SGN-40 in patients with relapsed DLBCL is planned.