Mucocutaneous side effects of Brequinar sodium. A new inhibitor of pyrimidine de novo biosynthesis

Pyrimidine depletion enhances targeted and immune therapy combinations in acute myeloid leukemia

Acute myeloid leukemia (AML) is a fatal disease characterized by the accumulation of undifferentiated myeloblasts, and agents that promote differentiation have been effective in this disease but are not curative. Dihydroorotate dehydrogenase inhibitors (DHODHi) have the ability to promote AML differentiation and target aberrant malignant myelopoiesis. We introduce HOSU-53, a DHODHi with significant monotherapy activity, which is further enhanced when combined with other standard-of-care therapeutics. We further discovered that DHODHi modulated surface expression of CD38 and CD47, prompting the evaluation of HOSU-53 combined with anti-CD38 and anti-CD47 therapies, where we identified a compelling curative potential in an aggressive AML model with CD47 targeting. Finally, we explored using plasma dihydroorotate (DHO) levels to monitor HOSU-53 safety and found that the level of DHO accumulation could predict HOSU-53 intolerability, suggesting the clinical use of plasma DHO to determine safe DHODHi doses. Collectively, our data support the clinical translation of HOSU-53 in AML, particularly to augment immune therapies. Potent DHODHi to date have been limited by their therapeutic index; however, we introduce pharmacodynamic monitoring to predict tolerability while preserving antitumor activity. We additionally suggest that DHODHi is effective at lower doses with select immune therapies, widening the therapeutic index.

Mucocutaneous reactions to chemotherapy

Chemotherapeutic agents are a widely used treatment modality. Side effects range from common to unusual and may be confused with other cutaneous sequelae of oncologic treatment. The goal of this communication is to elaborate on previous descriptions of the cutaneous manifestations of chemotherapeutic treatment and to discuss more recent findings.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be able to generate a differential diagnosis of possible etiologies for varying patterns of cutaneous involvement in patients receiving chemotherapy and identify the various cutaneous side effects of chemotherapeutic treatment. In addition, they should be able to distinguish life-threatening side effects that require immediate management from more benign manifestations of chemotherapeutic treatment.

The development of Brequinar as an immunosuppressive drug for transplantation

The preclinical and clinical characterization of Brequinar sodium has demonstrated the potential for the use of this drug as a component of a polytherapeutic treatment strategy to prevent the rejection of organ grafts. Brequinar, along with several other new immunosuppressive drugs, including Mizorbine, 15-deoxyspergualin, and Mycophenolate mofetil, is an antimetabolite with immunosuppressive activity and toxic side effects that are distinctly different from those of CsA and the newly characterized FK 506. This combination of effective antiproliferative activity exhibited by these newer agents and the well-established effect of CsA on T-lymphocyte activation offers the potential for the development of immunosuppressive regimens that are significantly more effective with fewer side effects for the patient. The concept of synergistic interaction between these two classes of immunosuppressive agents has been tested experimentally and found to be extremely effective for both allograft and xenograft models of graft rejection (Cosenza et al. 1993, 1993a, Stepkowski & Kahan 1993). It remains to be established that a similar synergism will exist for clinical transplantation. The effectiveness of CsA as a primary immunosuppressive agent, however, assures the inclusion of CsA in any polytherapeutic approach to be tested in the near future. New clinical trials designed to prove efficacy for immunosuppressive agents, such as BQR, will use CsA or FK 506 as a primary component of the treatment protocol. The combination of immunosuppressive agents that will eventually be applied in wide clinical use is not clear. While some new immunosuppressive agents have been more extensively tested clinically, BQR exhibits a number of unique features that make this compound particularly attractive for inclusion in new immunosuppressive regimens. The drug is readily soluble in aqueous solutions and can be administered intravenously or orally with equal effectiveness. Brequinar exhibits a high level of bioavailability following oral administration and an extended half-life that permits less frequent administration. While the metabolic byproducts of BQR have not been clearly described, there is good evidence that the parent compound exhibits the majority, if not all, of the immunosuppressive activity. The ability to monitor the parent drug directly or measure the depletion of enzyme products that reflect the activity of the drug are important features of the drug that simplify its use in a clinical setting. Although BQR exhibits important adverse side effects at high doses, the effects of the drug are characteristic of antimetabolites and are therefore predictable, constant, and reversible.(ABSTRACT TRUNCATED AT 400 WORDS)

Phase I and pharmacokinetic study of brequinar (DUP 785; NSC 368390) in cancer patients

Brequinar (DUP 785, NSC 368390) is a 4-quinoline carboxylic acid derivative with broad spectrum antitumour activity in experimental models that acts as an antimetabolite by specific inhibition of de novo pyrimidine synthesis. We performed a phase I study of brequinar administered as a 10 min intravenous (i.v.) infusion for 5 consecutive days, every 4 weeks. 67 evaluable patients were entered in this study and a total of 130 courses were administered at doses ranging from 2 to 350 mg/m2. The dose-limiting toxicity was myelosuppression with predominant thrombocytopenia. Myelosuppression was dose-related and non-cumulative, with considerable interpatient variability depending on haematological risk factors. The maximum tolerated dose of brequinar was 210 mg/m2/day in poor risk patients whereas patients with good risk haematological profile tolerated higher doses (up to 350 mg/m2/day). Other non-limiting toxicities included nausea and vomiting, mucositis and skin reactions. Brequinar plasma pharmacokinetic profiles were biphasic with alpha half-life ranging from 0.1 to 0.7 h, and beta half-life ranging from 1.5 to 8.2 h. Increase in brequinar area under the plasma concentration versus time curves (AUC) was nonlinear. Day 5 brequinar pharmacokinetics obtained in 21 patients indicated a significant increase in AUC (47%) and half-life beta (133%) compared to day 1 pharmacokinetics in the same patient. Brequinar plasma AUC and the per cent change in platelet count at nadir were correlated (P < 0.001). Although no objective response was observed in this study, one minor response was noted in cervical lymph nodes of a Hodgkin's disease patient.

Multicenter phase II trial of brequinar sodium in patients with advanced squamous-cell carcinoma of the head and neck

A total of 19 patients with advanced squamous-cell carcinoma of the head and neck who had not previously been exposed to chemotherapy were treated with brequinar sodium as first-line chemotherapy. Brequinar was given intravenously at a median weekly dose of 1,200 mg/m2. The toxicity was moderate, with 7 patients (37%) experiencing grade 3 or 4 toxicity. In all, 16 patients who were evaluable for efficacy showed no objective response. We conclude that brequinar given at this dose and on this schedule has no significant activity in advanced squamous-cell carcinoma of the head and neck.