Evaluating the adverse effects of melphalan formulations.

INTRODUCTION: For multiple myeloma patients who respond to primary therapy, autologous hematopoietic stem cell transplant (HSCT) is considered standard of care with high-dose melphalan for transplant candidates. There are now two different melphalan formulations available, including a propylene glycol containing (PG-MEL) product and a propylene glycol-free (PG-free MEL) product. Although considered bioequivalent, there remains limited literature directly evaluating the adverse events between the two agents. We seek to assess the tolerability and severity of side effects between the two formulations in a real-life practice setting. METHODS: A retrospective, descriptive analysis was conducted of multiple myeloma patients who received autologous stem cell conditioning with either melphalan formulation when dosed at 100 mg/m2/dose for two consecutive doses. The primary outcome was the assessment of tolerability and severity of side effects. Tolerability was split into four major categories including hematologic toxicity, gastrointestinal toxicity, renal toxicity, and highest recorded mucositis grade. RESULTS: There were a total of 78 patients who received a melphalan preparation during the study. The median time to myeloablation and neutrophil engraftment was five and seven days post-HSCT, respectively, for all patients. Patients who received PG-free MEL were less likely to develop mucositis, with 22 (56%) reported highest grade 0, defined by World Health Organization oral toxicity scale, compared to those who received PG-MEL (33%), p = 0.04. CONCLUSION: There were minimal differences in tolerability or side effects observed between PG-free MEL and PG-MEL. These data may assist in better understanding the anticipated adverse effects of a high-dose melphalan conditioning therapy.

The Myeloablative Drug Busulfan Converts Cysteine to Dehydroalanine and Lanthionine in Redoxins.

The myeloablative agent busulfan (1,4-butanediol dimethanesulfonate) is an old drug that is used routinely to eliminate cancerous bone marrow prior to hematopoietic stem cell transplant. The myeloablative activity and systemic toxicity of busulfan have been ascribed to its ability to cross-link DNA. In contrast, here we demonstrate that incubation of busulfan with the thiol redox proteins glutaredoxin or thioredoxin at pH 7.4 and 37 °C results in the formation of putative S-tetrahydrothiophenium adducts at their catalytic Cys residues, followed by ß-elimination to yield dehydroalanine. Both proteins contain a second Cys, in their catalytic C-X-X-C motif, which reacts with the dehydroalanine, the initial Cys adduct with busulfan, or the S-tetrahydrothiophenium, to form novel intramolecular cross-links. The reactivity of the dehydroalanine (DHA) formed is further demonstrated by adduction with glutathione to yield a lanthionine and by a novel reaction with the reducing agent tris(2-carboxyethyl)phosphine (TCEP), which yields a phosphine adduct via Michael addition to the DHA. Formation of a second quaternary organophosphonium salt via nucleophilic substitution with TCEP on the initial busulfan-protein adduct or on the THT(+)-Redoxin species is also observed. These results reveal a rich potential for reactions of busulfan with proteins in vitro, and likely in vivo. It is striking that several of the chemically altered protein products retain none of the atoms of busulfan, in contrast to typical drug-protein adducts or traditional protein modification reagents. In particular, the ability of a clinically used drug to convert Cys to dehydrolanine in intact proteins, and its subsequent reaction with biological thiols, is unprecedented.

A Phase IIb, Multicenter, Open-Label, Safety, and Efficacy Study of High-Dose, Propylene Glycol-Free Melphalan Hydrochloride for Injection (EVOMELA) for Myeloablative Conditioning in Multiple Myeloma Patients Undergoing Autologous Transplantation.

Autologous stem cell transplantation (ASCT) after high-dose melphalan conditioning is considered a standard of care procedure for patients with multiple myeloma (MM). Current formulations of melphalan (eg, Alkeran for Injection [melphalan hydrochloride]; GlaxoSmithKline, Research Triangle Park, NC, USA) have marginal solubility and limited chemical stability upon reconstitution. Alkeran requires the use of propylene glycol as a co-solvent, which itself has been reported to cause such complications as metabolic/renal dysfunction and arrhythmias. EVOMELA (propylene glycol-free melphalan HCl; Spectrum Pharmaceuticals, Inc., Irvine, CA, USA) is a new i.v. melphalan formulation that incorporates Captisol (Ligand Pharmaceuticals, Inc., La Jolla, CA, USA), a specially modified cyclodextrin that improves the solubility and stability of melphalan and eliminates the need for propylene glycol. This new formulation has been shown to be bioequivalent to Alkeran. EVOMELA (200 mg/m(2)) was administered as 2 doses of 100 mg/m(2) each in a phase IIb, open-label, multicenter study to confirm its safety and efficacy as a high-dose conditioning regimen for patients with MM undergoing ASCT. At 5 centers, 61 patients (26 women) with a median age of 62 years (range, 32-73) were enrolled. All patients achieved myeloablation with a median time of 5 days post-ASCT, and all successfully achieved neutrophil and platelet engraftment with median times of 12 days post-ASCT and 13 days post-ASCT, respectively; treatment-related mortality on day 100 was 0%. Overall response rate (according to independent, blinded review) was high (100%), with an overall complete response rate of 21% (13% stringent complete response; 8% complete response) and overall partial response rate of 79% (61% very good partial response; 18% partial response). The incidence of grade 3 mucositis and stomatitis was low (10% and 5%, respectively) with no grade 4 mucositis or stomatitis reported (graded according to National Cancer Institute Common Terminology Criteria for Adverse Events). Based on investigators' assessment of mucositis using the World Health Organization (WHO) oral toxicity scale, 75% of patients had a shift in mucositis score from WHO grade 0 at baseline to a higher grade on study, of which 13% of patients reported WHO grade 3 as the worst post-treatment mucositis over the course of the study; there were no reports of WHO grade 4 mucositis during the study. This study confirms the efficacy and acceptable safety profile of EVOMELA, a new propylene glycol-free melphalan formulation, as a high-dose conditioning regimen for ASCT in patients with MM.

High-dose treosulfan in conditioning prior to hematopoietic stem cell transplantation.

IMPORTANCE OF THE FIELD: Despite the marked development in the field of preparative regimens prior to hematopoietic stem cell transplantation (HSCT) over the last decade, the search for a superior conditioning agent is still continuing. In view of the literature reports, treosulfan (TREO), a structural analog of busulfan (BU), appears to be a promising candidate in terms of myeloablative, immunosuppressive and antimalignancy effects as well as low organ toxicity. AREAS COVERED IN THIS REVIEW: The article focuses on pharmacological activity, pharmacokinetics and toxicity of TREO. Compressed description of the drug-based conditioning prior to HSCT is also presented. Finally, TREO and BU characteristics are compared. Specific information of TREO concerning pediatric and adult patients is provided throughout the whole paper. The data refer predominantly to the publications, in majority from the last 10 years. WHAT THE READER WILL GAIN: According to our best knowledge, the paper is the first such comprehensive review on TREO, especially in terms of its application in pediatric HSCT. TAKE HOME MESSAGE: TREO offers a great potential as a conditioning agent prior to HSCT but further investigations of the drug are warranted to clearly verify its advantages. However, we expect TREO to be registered as a novel conditioning agent in the near future.