A Phase I-II Pilot Study of Divalproex Sodium Alone and in Combination with All-Trans-Retinoic Acid (ATRA) in Relapsed or Refractory Acute Myeloid Leukemia.

Valproic acid (VPA), acetylates histones, induces apoptosis and synergizes with All Trans Retinoic Acid (ATRA), in promoting G1 arrest and leukemic cell differentiation in vitro. Based on these observations we designed a Phase I/II pilot study of VPA alone and in combination with ATRA in patients with relapsed, refractory or poor risk acute myeloid leukemia (AML). VPA was initiated at 15mg/kg/day (day 1 IV followed by daily po) and escalated weekly by 10mg/kg (max 60 mg/kg/day) targeted to reach a serum concentration of 80–120mg/ml. For the combination, ATRA was to be added initially at 25mg/M2/day (first 3 patients) and titrated, in the absence of toxicity, to 45mg/M2/day, in two divided doses, following a minimum of 7 days of VPA therapy alone. Treatment was planned to continue for 45 days following achievement of a VPA level of >80mg/ml on two separate, consecutive measurements. To date we have treated 8 patients (7 tAML/MDS, 1 de novo AML) with VPA alone. Two of 8 additional patients to be treated with VPA + ATRA (1 tAML/ET; 1 tAML/MDS), are too early in their treatment upon which to report. Of the VPA alone treated patients, Median age was 63 (range 52–78). No Prior therapy: 3/8 pts; 5F:3M; ECOG PS 0 (1), 1 (5), 2 (2);Cytogenetic abnormalities: normal (1); t(3;18) (1); complex karyotype (6), including trisomy 8 (3), abnormalities of 11 (2) or monosomy 7 (2). Baseline bone marrow blast percentage > 50%; (8); median bone marrow cellularity 84% (range 35–90). Treatment: Median duration of treatment 45 days (range 19–99). Therapy discontinued before 45 days; withdrawl (2); death at home on study (day 33 of treatment), (1); reversible grade 3 toxicity(2). VPA levels: Serum concentrations of VPA of > 80mg/ml was achieved in all patients; Hematologic effects: Changes in CBC: increase in WBC, ANC and blast count (BLC)(3), followed by decrease in WBC and BLC (2); increase in WBC/ANC &decrease in BLC (1); decrease in WBC, ANC and BLC (3); &initial decrease in BLC &increase in ANC (1). Marrow: decrease in marrow cellularity (2)( 90% to 30%); loss of detectable trisomy 8 population (1); &decrease in bone marrow blasts (1) (64% to 5%) was observed. One patient reverted back to MDS, lasting 5 months. Side Effects: somnolence (grade 2–4) was observed in 4/8 patients, and was the major cause of withholding treatment. We also observed a constellation of symptoms (weight gain, fever, elevated WBC, shortness of breath, elevated LDH, bone pain) and chest x-ray findings consistent with &reminiscent of APL syndrome, within seven days of achieving the targeted serum VPA levels (> 80mg/ml), in 2 pts. Decadron was started two days (1) and immediately (1) following the onset of symptoms: signs and symptoms abated quickly &resolved subsequently within three days. In retrospect, one additional patient had comparable symptoms, for which VPA was stopped, following admission to an outside hospital for fever, pulmonary infiltrates and altered mental status. Correlative studies: serial assessment of bulk histone acetylation (H3, H4) was performed in all 8 patients. 7/8 patients showed evidence of histone hyperacetylation in mononuclear cells from peripheral blood, during treatment with VPA. Additional patients are being treated with VPA + ATRA. Analysis of these studies will be forthcoming.