Purpose: We demonstrated previously that sera from quinine-treated patients reversed the multidrug resistance (MDR) of a human leukemic cell line. We now report a phase I and II clinical study that examined the toxicity of the combination of quinine with mitoxantrone and cytarabine (Ara-C).
Patients and methods: Fifteen adult patients with relapsed or refractory acute leukemia were treated with quinine formiate (30 mg/kg/d in continuous intravenous (IV) infusion from day 1 through day 5 or 6) associated with Ara-C (1 g/m2 in 3-hour IV infusion twice a day for 5 days) and five increasing doses of mitoxantrone (from 8 mg/m2/d for 4 days to 12 mg/m2/d for 5 days).
Results: The main toxicity was severe myelosuppression: the mean times to leukocyte recovery (> 500/microL), granulocytes recovery (> 500/microL), and platelet count recovery (> 50,000/microL) were 23 days (range, 17 to 29 days), 30.6 days (range, 17 to 48 days), and 35.4 days (range, 14 to 75 days), respectively. The nonhematopoietic toxicity of this regimen was acceptable. Nausea and vomiting were common, but severe mucositis was observed in only two patients. Cardiotoxicity was limited to transient episodes of moderate supraventricular tachycardia and a clinically well-tolerated bradycardia. Tinnitus and vertigo were observed in 10 cases (67%), and mild hearing loss and transient increase of serum bilirubin were observed in six patients (40%). Total quinine serum levels reached a steady-state concentration between 6.4 and 18 mg/L in 24 hours. Complete remission (CR) was achieved in eight of 14 (57%) assessable patients, and partial response (PR) was achieved in two additional patients (14%). P-glycoprotein expression was detected on blast cells from five of 13 studied patients before treatment. A response was observed in all P-glycoprotein-positive cases.
Conclusion: Quinine can be used safely as a potential reversing agent of MDR for the treatment of clinically resistant acute leukemias.