Verena Karsten

Cloretazine (VNP40101M), a Novel Sulfonylhydrazine Alkylating Agent, in Patients Age 60 Years or Older With Previously Untreated Acute Myeloid Leukemia

PURPOSE Cloretazine (VNP40101M) is a sulfonylhydrazine alkylating agent with significant antileukemia activity. A multicenter phase II study of cloretazine was conducted in patients 60 years of age or older with previously untreated acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). PATIENTS AND METHODS Cloretazine 600 mg/m2 was administered as a single intravenous infusion. Patients were stratified by age, performance score, cytogenetic risk category, type of AML, and comorbidity. RESULTS One hundred four patients, median age 72 years (range, 60 to 84 years), were treated on study. Performance status was 2 in 31 patients (30%) and no patient had a favorable karyotype. Forty-seven patients (45%) had cardiac disease, 25 patients (24%) had hepatic disease, and 19 patients (18%) had pulmonary disease, defined as per the Hematopoietic Cell Transplantation-Specific Comorbidity Index, at study entry. The overall response rate was 32%, with 29 patients (28%) achieving complete response (CR) and four patients (4%) achieving CR with incomplete platelet recovery. Response rates in 44 de novo AML patients, 45 secondary AML patients, and 15 high-risk MDS patients were 50%, 11%, and 40%, respectively. Response by cytogenetic risk category was 39% in 56 patients with intermediate cytogenetic risk and 24% in 46 patients with unfavorable cytogenetic risk. Nineteen (18%) patients died within 30 days of receiving cloretazine therapy. Median overall survival was 94 days, with a 1-year survival of 14%; the median duration of survival was 147 days, with a 1-year survival of 28% for those who achieved CR. CONCLUSION Cloretazine has significant activity and modest extramedullary toxicity in elderly patients with AML or high-risk MDS. Response rates remain consistent despite increasing age and comorbidity.

Single-Agent Laromustine, A Novel Alkylating Agent, Has Significant Activity in Older Patients With Previously Untreated Poor-Risk Acute Myeloid Leukemia

PURPOSE An international phase II study of laromustine (VNP40101M), a sulfonylhydrazine alkylating agent, was conducted in patients age 60 years or older with previously untreated poor-risk acute myeloid leukemia (AML). PATIENTS AND METHODS Laromustine 600 mg/m(2) was administered as a single 60-minute intravenous infusion. Patients were age 70 years or older or 60 years or older with at least one additional risk factor-unfavorable AML karyotype, Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 2, and/or cardiac, pulmonary, or hepatic comorbidities. Results Eighty-five patients (median age, 72 years; range, 60 to 87 years) were treated. Poor-risk features included age 70 years or older, 78%; adverse karyotype, 47%; PS of 2, 41%; pulmonary disease, 77%; cardiac disease, 73%; and hepatic disease, 3%. Ninety-six percent of patients had at least two risk factors, and 39% had at least four risk factors. The overall response rate (ORR) was 32%, with 20 patients (23%) achieving complete response (CR) and seven (8%) achieving CR with incomplete platelet recovery (CRp). ORR was 20% in patients with adverse cytogenetics; 32% in those age 70 years or older; 32% in those with PS of 2; 32% in patients with baseline pulmonary dysfunction; 34% in patients with baseline cardiac dysfunction; and 27% in 33 patients with at least four risk factors. Twelve (14%) patients died within 30 days of receiving laromustine therapy. Median overall survival was 3.2 months, with a 1-year survival of 21%; the median duration of survival for those who achieved CR/CRp was 12.4 months, with a 1-year survival of 52%. CONCLUSION Laromustine has significant single-agent activity in elderly patients with poor-risk AML. Adverse events are predominantly myelosuppressive or respiratory. Response rates are consistent across a spectrum of poor-risk features.

Phase I Study of Cloretazine (VNP40101M), a Novel Sulfonylhydrazine Alkylating Agent, Combined with Cytarabine in Patients with Refractory Leukemia

Purpose: Cloretazine (VNP40101M) is a novel sulfonylhydrazine alkylating agent with significant antileukemia activity. A phase I study of cloretazine combined with cytarabine (1-β-d-arabinofuranosylcytosine, ara-C) was conducted in patients with refractory disease. Design: Ara-C was given i.v. at a fixed dose of 1.5 gm/m2/d by continuous infusion for 4 days (patients ages <65 years at time of diagnosis) or 3 days (patients ages ≥65 years). Cloretazine was given i.v. over 15 to 60 minutes on day 2 at a starting dose of 200 mg/m2, with escalation in 100 mg/m2 increments in cohorts of three to six patients until a maximum tolerated dose was established. The DNA repair enzyme O6-alkylguanine DNA alkyltransferase (AGT) was measured at baseline. Results: Forty patients, including 32 with acute myeloid leukemia, received 47 courses of treatment. Complete responses were seen at cloretazine dose levels of ≥400 mg/m2 in 10 of 37 (27%) evaluable patients, and in this patient subset, AGT activity was significantly lower in patients that responded to treatment than in patients who did not (P ≤ 0.027). Dose-limiting toxicities (gastrointestinal and myelosuppression) were seen with 500 and 600 mg/m2 of cloretazine combined with the 4-day ara-C schedule but not seen with the 3-day schedule. Conclusion: The recommended cloretazine dose schedule for future studies is 600 mg/m2 combined with 1.5 gm/m2/d continuous infusion of ara-C for 3 days. The cloretazine and ara-C regimen has significant antileukemic activity. AGT activity may be a predictor of response to cloretazine.

Phase I trial of VNP40101M (Cloretazine) in children with recurrent brain tumors: a pediatric brain tumor consortium study.

Purpose: VNP40101M (Cloretazine), a novel DNA alkylating agent, was evaluated in a phase I study in children with recurrent brain tumors. Experimental Design: VNP40101M was given i.v. daily for 5 consecutive days every 6 weeks for up to eight cycles. Dose escalation was done independently in patients stratified based on intensity of prior therapy (moderately pretreated, stratum I; heavily pretreated, stratum II). Correlative studies included pharmacokinetics and measurement of O6-alkylguanine-DNA alkyl transferase levels in peripheral blood mononuclear cells before and after treatment. Results: Forty-one eligible patients (stratum I, 19; stratum II, 22) were enrolled on this study. The dose-limiting toxicity in 35 evaluable patients was myelosuppression, which occurred in 4 of 16 patients in stratum I and 3 of 19 patients in stratum II. Pharmacokinetic studies showed a median terminal half-life of 30 min (range, 14-39.5). The maximum tolerated dose in stratum I and II were 45 and 30 mg/m2/d daily for 5 days every 6 weeks, respectively. Peripheral blood mononuclear cells alkylguanine alkyl transferase levels did not decrease significantly after VNP40101M treatment. Central imaging review confirmed that three patients had stable disease for a median of 45 weeks (range, 37-61+) after therapy. Conclusions: The recommended dose of VNP40101M for phase II studies in children with brain tumors is 45 mg/m2/d in moderately pretreated and 30 mg/m2/d in heavily pretreated patients when administered for 5 consecutive days every 6 weeks.

msbB deletion confers acute sensitivity to CO2 in Salmonella enterica serovar Typhimurium that can be suppressed by a loss-of-function mutation in zwf

BackgroundPathogens tolerate stress conditions that include low pH, oxidative stress, high salt and high temperature in order to survive inside and outside their hosts. Lipopolysaccharide (LPS), which forms the outer-leaflet of the outer membrane in Gram-negative bacteria, acts as a permeability barrier. The lipid A moiety of LPS anchors it to the outer membrane bilayer. The MsbB enzyme myristoylates the lipid A precursor and loss of this enzyme, in Salmonella, is correlated with reduced virulence and severe growth defects that can both be compensated with extragenic suppressor mutations.ResultsWe report here that msbB (or msbB somA) Salmonella are highly sensitive to physiological CO2 (5%), resulting in a 3-log reduction in plating efficiency. Under these conditions, msbB Salmonella form long filaments, bulge and lyse. These bacteria are also sensitive to acidic pH and high osmolarity. Although CO2 acidifies LB broth media, buffering LB to pH 7.5 did not restore growth of msbB mutants in CO2, indicating that the CO2-induced growth defects are not due to the effect of CO2 on the pH of the media. A transposon insertion in the glucose metabolism gene zwf compensates for the CO2 sensitivity of msbB Salmonella. The msbB zwf mutants grow on agar, or in broth, in the presence of 5% CO2. In addition, msbB zwf strains show improved growth in low pH or high osmolarity media compared to the single msbB mutant.ConclusionThese results demonstrate that msbB confers acute sensitivity to CO2, acidic pH, and high osmolarity. Disruption of zwf in msbB mutants restores growth in 5% CO2 and results in improved growth in acidic media or in media with high osmolarity. These results add to a growing list of phenotypes caused by msbB and mutations that suppress specific growth defects.

Phase I Study of Temozolomide and Laromustine (VNP40101M) in Patients With Relapsed or Refractory Leukemia

PURPOSE Although alkylators are known to be effective against some myeloid leukemias, resistance is often mediated via O6-alkylguanine-DNA alkyltransferase (AGT). Temozolomides inhibition of AGT may sensitize leukemia cells to the novel alkylator laromustine. We conducted a phase I translational study to evaluate the toxicities and estimate the maximum tolerated dose (MTD) of laromustine when administered with temozolomide (TMZ) in patients with hematologic malignancies. PATIENTS AND METHODS TMZ was delivered twice daily for 5 doses followed by a single infusion of laromustine. The target TMZ dose was the dose that would reliably result in > 90% AGT depletion. Once the target TMZ dose was identified, the laromustine dose was escalated. A total of 35 patients with relapsed/refractory leukemia were treated. RESULTS Treatment with TMZ 300 mg for 5 doses resulted in > 90% depletion of AGT levels in 5 of 6 patients. The MTD of the combination was established at TMZ 1500 mg and laromustine 300 mg/m2. Three of the 7 patients assayed from cohort 1 achieved > 90% depletion of AGT activity (range, 77%-100% depletion; median, 88%). Five of 6 patients enrolled in cohort 2 achieved > 90% depletion of AGT activity (range, 92%-100% depletion; median, 93.5%). This established that the 300-mg dose of TMZ (1500 mg total) would be maintained in subsequent cohorts. The majority of adverse events were primarily hematologic, with infectious and pulmonary complications also noted. Three (9%) of the patients with previous refractory disease achieved a complete remission, and 5 (14%) of the patients achieved a morphologic, leukemia-free, but persistent hypocellular bone marrow status. CONCLUSION Laromustine in combination with TMZ is tolerable and manageable at doses that predictably suppress AGT. Reliable TMZ-induced inhibition of AGT was observed in doses that are clinically tolerable. Evidence of antitumor effect was observed with this combination, suggesting that further efficacy studies should be performed.