We're Not "DON" Yet: Optimal Dosing and Prodrug Delivery of 6-Diazo-5-oxo-L-norleucine.

The broadly active glutamine antagonist 6-diazo-5-oxo-L-norleucine (DON) has been studied for 60 years as a potential anticancer therapeutic. Clinical studies of DON in the 1950s using low daily doses suggested antitumor activity, but later phase I and II trials of DON given intermittently at high doses were hampered by dose-limiting nausea and vomiting. Further clinical development of DON was abandoned. Recently, the recognition that multiple tumor types are glutamine-dependent has renewed interest in metabolic inhibitors such as DON. Here, we describe the prior experience with DON in humans. Evaluation of past studies suggests that the major impediments to successful clinical use included unacceptable gastrointestinal (GI) toxicities, inappropriate dosing schedules for a metabolic inhibitor, and lack of targeted patient selection. To circumvent GI toxicity, prodrug strategies for DON have been developed to enhance delivery of active compound to tumor tissues, including the CNS. When these prodrugs are administered in a low daily dosing regimen, appropriate for metabolic inhibition, they are robustly effective without significant toxicity. Patients whose tumors have genetic, metabolic, or imaging biomarker evidence of glutamine dependence should be prioritized as candidates for future clinical evaluations of novel DON prodrugs, given either as monotherapy or in rationally directed pharmacologic combinations. Mol Cancer Ther; 17(9); 1824-32. ©2018 AACR.

Reviving Lonidamine and 6-Diazo-5-oxo-L-norleucine to Be Used in Combination for Metabolic Cancer Therapy.

Abnormal metabolism is another cancer hallmark. The two most characterized altered metabolic pathways are high rates of glycolysis and glutaminolysis, which are natural targets for cancer therapy. Currently, a number of newer compounds to block glycolysis and glutaminolysis are being developed; nevertheless, lonidamine and 6-diazo-5-oxo-L-norleucine (DON) are two old drugs well characterized as inhibitors of glycolysis and glutaminolysis, respectively, whose clinical development was abandoned years ago when the importance of cancer metabolism was not fully appreciated and clinical trial methodology was less developed. In this review, a PubMed search using the words lonidamine and 6-diazo-5-oxo-L-norleucine (DON) was undertaken to analyse existing information on the preclinical and clinical studies of these drugs for cancer treatment. Data show that they exhibit antitumor effects; besides there is also the suggestion that they are synergistic. We conclude that lonidamine and DON are safe and potentially effective drugs that need to be reevaluated in combination as metabolic therapy of cancer.

Phase II trial of 6-diazo-5-oxo-L-norleucine versus aclacinomycin-A in advanced sarcomas and mesotheliomas.

Ninety-eight patients with previously-treated advanced soft tissue sarcoma, bone sarcoma, or mesothelioma were randomly assigned to one of two intravenous single-agent treatment regimens, either 6-diazo-5-oxo-l-norleucine (DON; brief infusions of 50 mg/m2/day for 5 consecutive days every 4 weeks) or aclacinomycin-A (ACM-A, as 30-min infusions of 100 mg/m2 or 85 mg/m2, administered every 3 weeks). Of 43 patients who were evaluable for response, survival and toxicity, there were two responses (5%) produced by ACM-A; one in a male with mesothelioma, and one in a female with malignant fibrous histiocytoma. None of the 36 evaluable patients treated with DON developed an objective tumor response. Median survival was 4.8 months in the DON treatment arm, and 6.8 months in the ACM-A treatment arm. No patients on the DON arm experienced lethal or life-threatening toxicities, and severe toxicities resulting from this treatment included nausea and emesis (10%), stomatitis (2%), gastrointestinal toxicity (2%), and anemia (2%). Moderate toxicities included vomiting (24%), hematologic toxicity (24%), neurologic toxicity (7%), diarrhea (7%), mucositis (5%), fever (5%), palpitations (2%), hepatotoxicity (2%), bleeding (2%) and edema (2%). Fifteen percent experienced at least one severe reaction, and 63% experienced at least one moderate or greater toxicity. ACM-A was associated with four cases of life-threatening myelosuppression (7%); severe toxicities included myelosuppression (11%), neurologic toxicity (4%), diarrhea (2%), respiratory toxicity (2%), pain and muscle spasms (2%), edema (2%), and ulceration following extravasation (2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic and phase I study of intravenous DON (6-diazo-5-oxo-L-norleucine) in children.

DON (6-diazo-5-oxo-L-norleucine), a glutamine antagonist, has been subjected to limited clinical trials since 1957. Use of the drug in adults has been curtailed due to sparse reports of effectiveness as well as its dose-limiting toxicities, i.e., severe nausea, vomiting and mucositis. In earlier studies, children given DON orally in combination with 6-mercaptopurine had significant prolongation of remission of acute leukemias during maintenance therapy. As DON is acid-labile and relatively unstable in solution, oral administration does not appear to be ideal for DON. In the trial described in this report, i.v. DON therapy was studied, using i.v. chlorpromazine to control vomiting, in 20 children, 17 of whom were evaluable following treatment at DON dose levels ranging from 150 mg/m2 to 520 mg/m2. Nausea and vomiting, the dose-limiting toxicity for adults, was controlled with chlorpromazine. Mucositis, which has also been observed in adults, did not occur in the children given DON i.v. A maximum tolerated dose was not defined; however, the projected maximum tolerated dose appears to be in excess of 450 mg/m2. DON was measured in plasma using a rapid-sampling HPLC procedure. The total body clearance, plasma t1/2, and area under the plasma concentration curve (AUC) were calculated using a noncompartmental method. The drug is rapidly cleared from plasma (t 1/2 = 3 h), and its volume of distribution is approximately twice that of total body water in children. These pharmacokinetic data, differ from that of adults reported by others. Specifically, the plasma t 1/2 for children is longer: total body clearance (Cl), and volume of distribution at steady state (Vss) are greater. In addition, no dose dependency of t 1/2, Cl or Vss was observed in this study, and the DON pharmacokinetics were linear and predictable. Five of nine children with acute leukemia showed improvement, though insufficient for classification as partial response, and five of eight children with solid tumors also showed improvement. Further trials using DON in combination with thiopurines or other agents appear indicated.

Phase II evaluation of DON (6-diazo-5-oxo-L-norleucine) in patients with advanced colorectal carcinoma.

Twenty-three patients with advanced colorectal carcinoma, previously treated with chemotherapy, were entered in a phase II trial of DON (6-Diazo-5-Oxo-L-Norleucine), an antagonist of L-glutamine. One of 14 adequately treated patients had a partial response of 6 weeks duration. The dose-limiting toxicity was nausea and vomiting; 48% of patients originally entered on the study withdrew because of vomiting. Myelosuppression was minimal, with only mild thrombocytopenia noted. The dose and schedule used in this study were beyond the maximally tolerated dose for many patients; future phase II studies of DON will be difficult to complete unless schedules and doses are found which result in less nausea and vomiting.

Phase I and pharmacokinetic studies of DON.

DON, a glutamine antagonist, was administered iv to 26 patients with advanced cancer either once every 3 wks or daily for 3 days every 3 wks to determine toxicity and to look for evidence of therapeutic effect. Total doses ranged from 150 to 600 mg/m2. The single-day schedule produced intolerable nausea and vomiting and no evidence of cytotoxicity at 450-550 mg/m2 given over 10 mins or over 4 hrs. On the 3-day schedule, patients had tolerable gastrointestinal toxic effects at total doses up to 480 mg/m2 given in three equally divided doses by 10-min infusion. This dose also produced cytotoxic activity manifested as transient mild leukopenia and, rarely, thrombocytopenia. No objective responses were seen. Analysis of the plasma elimination of DON demonstrated dose-dependent pharmacokinetic behavior. The parent compound was not detectable in the urine of any patient, indicating extensive metabolism of the drug.

Phase I study of 6-diazo-5-oxo-L-norleucine (DON).

We conducted a phase I study of 6-diazo-5-oxo-L-norleucine given iv on a twice weekly schedule. Twenty-six evaluable patients received 31 courses of the drug. Doses ranged from 100 to 500 mg/m2. Nausea with vomiting was the dose-limiting toxic effect, transient thrombocytopenia was seen frequently, and mucositis occurred in 39% of the patients. No definite therapeutic responses were observed in 18 patients with measurable lesions. The recommended dose for phase II studies is 200-300 mg/m2 iv twice weekly.