Results of an earlier open-label pilot study showed that 4162W94 was a relatively non-depleting anti-CD4 monoclonal antibody that induced >80% down-modulation of CD4 molecules from the surface of T lymphocytes. This placebo-controlled repeat-cycle study was conducted in active rheumatoid arthritis (RA) patients to determine the duration of CD4 blockade required to achieve lasting clinical benefit.
Following DMARD washout, 48 patients (i.e. three cohorts of 16 patients) with ACR-defined RA were to be dosed with 1 (cohort 1), 2 (cohort 2) or 3 (cohort 3) cycles of 5x300 mg 4162W94 or placebo (12 and 4 patients per cohort respectively) at monthly intervals. There was at least 3 months of follow-up after dosing. Clinical outcome was assessed in evaluable patients (receiving at least 80% of each dose course) using ACR20 criteria (required on two consecutive visits). CD4 lymphocyte counts and adverse events were also monitored.
Sixteen patients were dosed in each of the first two cohorts; however, the dose was reduced in cohort 3 after five patients had received up to two dose cycles due to accumulating evidence of a high frequency of skin rash. These patients were analysed according to the number of cycles received. A further eight patients received 5x100 mg for one to three cycles prior to stopping the study for administrative reasons. Four of 13 (P=0.119 vs placebo) and 7/13 (P=0.015 vs placebo) in cohorts 1 and 2 respectively achieved ACR20 response on at least two consecutive occasions. No patient receiving 5x100 mg/day or placebo achieved ACR20. Four patients were still responding at the end of the 3-month follow-up period. CD4 lymphocyte suppression (<0.2x10(9)/l on at least two successive occasions) occurred in 11/34 patients who received 4162W94 vs none on placebo. Rash occurred in 21/34 monoclonal antibody-treated patients, including one case of biopsy-confirmed cutaneous vasculitis and 1/11 placebo patients.
4162W94 demonstrated significant clinical efficacy in this study. However, because of unacceptable CD4 lymphopenia and rash, the original hypothesis that prolonged CD4 blockade would give lasting clinical benefit was not tested.