Azithromycin concentrations during long-term regimen, a pilot study in patients with MALT lymphoma

In view of the antineoplastic effects of the macrolide clarithromycin in mucosa associated lymphatic tissue (MALT)-lymphoma, we performed a pilot study assessing levels of azithromycin in plasma, peripheral blood mononuclear cells (PBMC) and polymorphonuclear leukocytes (PMN) of MALT-lymphoma patients to determine the pharmacokinetics and potential influences of respective concentrations on the therapeutic outcome. In total 16 patients with MALT-lymphoma received 1.5 g of oral azithromycin once-weekly over 6 months. Blood was sampled directly prior to the following dose every 4 weeks during treatment. Drug levels were analysed by high performance liquid chromatography in plasma and intracellularly in PBMC and PMN. They were correlated with patients’ age, weight and body-mass-index and compared between patients responsive or unresponsive to treatment. Mean azithromycin plasma levels of all patients were 58.97 ± 30.48 ng/ml, remaining stable throughout the treatment period. Correlation analysis of plasma azithromycin showed no significance. Intracellular PBMC concentrations were 6648 ± 8479 ng/ml, without any significant difference between responders and non-responders. Mean PMN levels were 39,274 ± 25,659 ng/ml and significantly higher in patients unresponsive to treatment (t = 2.858, p = 0.017). Our drug regime led to continuously high plasma and exceedingly high intracellular concentrations of azithromycin in PBMC and PMN. Age, weight or body-mass-index had no significant influence on plasma levels and thence should not be considered in dosage finding. High AZM levels in PBMC did not lead to a better treatment response, whereas enrichment in PMN suggested a poorer outcome. The threshold for immunomodulatory effects on lymphoma cells might not have been reached. Additionally, the finding of stable plasma and intracellular concentrations over months with high-dose azithromycin administered in intervals might also be important for the further design of azithromycin-based trials against MALT-lymphoma. Trial registration: EudraCT 2016-001521-13, 14/06/2016.