Phase II trial of clarithromycin and pamidronate therapy in myeloma.

A phase II study to further evaluate any possible antimyeloma activity of clarithromycin was conducted following a report of possible clinical efficacy. Twenty patients, 11 male and 9 female with a median age of 73 yr, received clarithromycin 500 mg twice daily with monthly intravenous infusions of disodium pamidronate. None of the study patients received concomitant cytotoxic or steroid therapy. Ten patients had relapsed disease, five had refractory disease, four were previously untreated, and one patient was unsuitable for cytotoxic therapy. The median number of previous treatment modalities was 1.5. Serum M protein levels and urinary M protein excretion were monitored along with other parameters to assess response. Median duration of therapy was 16 wk and six patients had dose escalation. A significant decrease in M protein production occurred in one patient at wk 12 of therapy, which maximized following dose escalation to a 47% decrease from baseline. Two patients had incremental but unsustained M protein reductions. Serum/urine M protein levels remained static in six patients and rose in the remaining six evaluable patients. The M protein response rates in this study are much lower than those previously reported and do not confirm efficacy. In addition, the recently postulated antimyeloma activity of pamidronate may explain some of the M protein decreases.