Ibrahim El-Serafi

N,N‐dimethylacetamide (DMA) is an organic solvent, used in busulphan, iv‐formulation, (Busulfex). DMA is metabolized primarily to N‐methylacetamide (MMA) via CYP2E1. In the present study, we investigated the pharmacokinetics and toxicity of DMA and MMA in patients, mice and cell lines. In pediatric patients (6 months to 18 years) undergoing hematopoietic stem cell transplantation, the pharmacokinetics of DMA and MMA were followed during the 4‐days Busulfex conditioning (3.2–4 mg/kg, b.i.d). No accumulation of DMA was found; however, a significant increase in clearance and a significant decrease ( p < 0.005) in half‐lives by the end of treatment were observed which might indicate CYP2E1 autoinduction. Furthermore, continuous increases in plasma concentration of MMA were observed during treatment and a terminal half‐life of 15.2 ± 1.7 h was detected. Moreover, ALT was significantly ( p = 0.04) increased in > 61% of the patients after conditioning. Additionally, mice were treated with either dimethyl sulfoxide (DMSO), DMA, busulphan in DMSO, Busulfex or saline for 4 days. DMA‐treated mice showed elevated ALT and AST values. Interestingly, Busulfex administration did not alter mice liver enzymes. Busulphan in DMA showed higher cytotoxicity compared to busulphan in DMSO in HepG‐2, Huh‐7 and HL‐60 cells. The combination Bu‐DMA‐MMA exhibited increased cytotoxicity in a concentration‐dependent manner. In conclusion, Busulfex administration to pediatric patients resulted in an accumulation of MMA during the 4‐days treatment. Busulfex is less toxic compared to Bu dissolved in DMA. MMA addition to Bu in DMA showed higher cytotoxicity. Therefore, MMA with a relatively long half‐life may induce hepatotoxicity and/or interaction with subsequently administered drugs; thus further investigations are urgently warranted.

Busulphan (Bu) is used as a part of the conditioning regimen prior to HSCT. Neurotoxicity is one of Bu major adverse-effects. We investigated the kinetics of busulphan and its metabolites (tetrahydothiophene, tetrahydrothiophene-1-oxide, sulfolane, 3-OH-sulfolane) in patients and mice as well as the mechanisms underlying CNS-toxicity in mice. Busulphan metabolites were detectable in plasma and urine up to 72-h after the last Bu-dose. Sulfolane levels were high and reached maximum concentration at the time-point reported for the convulsions’ occurrence. Mice were treated with either busulphan or one of its metabolites, separately. Sulfolane treated-mice showed the highest brain exposure (AUC_brain/AUC_plasma). Seizures and hypothermia were observed after sulfolane administration, accompanied with a significant decrease in calbindin-28k concentrations in the brain. Behavior changes but no signs of convulsions were seen in mice treated with lower sulfolane doses. Moreover, a reduction of spontaneous events during whole-cell patch clamp recordings from pyramidal neurons was observed following bath application of sulfolane. In conclusion, these are the first results showing that sulfolane is the major cause of seizures and hypothermia. Sulfolane concentration in plasma mirrors its concentration in the brain. The role of calbindin-D28K in CNS-toxicity and susceptibility to future neurodegenerative diseases should be investigated.

In addition to their immunosuppressive effect, cytostatics conditioning prior to adoptive therapy such as chimeric antigen receptor (CAR) T cells may play a role in debulking and remodeling the tumor microenvironment. We investigated in vitro the killing efficacy and impact of treosulfan and fludarabine on ovarian cancer cells expressing mesothelin (MSLN) and effect on MSLN-targeting CAR T cells. Treosulfan and fludarabine had a synergetic effect on killing of SKOV3 and OVCAR4 cells. Sensitivity to the combination of treosulfan and fludarabine was increased when SKOV3 cells expressed MSLN and when OVCAR4 cells were tested in hypoxia, while MSLN cells surface expression by SKOV3 and OVCAR4 cells was not altered after treosulfan or fludarabine exposure. Exposure to treosulfan or fludarabine (10 µM) neither impacted MSLN-CAR T cells degranulation, cytokines production upon challenge with MSLN + OVCAR3 cells, nor induced mitochondrial defects. Combination of treosulfan and fludarabine decreased MSLN-CAR T cells anti-tumor killing in normoxia but not hypoxia. In conclusion, treosulfan and fludarabine killed MSLN + ovarian cancer cells without altering MSLN-CAR T cells functions (at low cytostatics concentration) even in hypoxic conditions, and our data support the use of treosulfan and fludarabine as conditioning drugs prior to MSLN-CAR T cell therapy.

Cyclophosphamide (Cy) is a prodrug that is mainly bioactivated by cytochrome P450 (CYP) 2B6 enzyme. Several other enzymes are also involved in its bioactivation and affect its kinetics. Previous studies have shown the effect of the enzymes’ genetic polymorphisms on Cy kinetics and its clinical outcome. These results were controversial primarily because of the involvement of several interacting enzymes in the Cy metabolic pathway, which can also be affected by several clinical factors as well as other drug interactions. In this review article, we present the effect of CYP2B6 polymorphisms on Cy kinetics since it is the main bioactivating enzyme, as well as discussing all previously reported enzymes and clinical factors that can alter Cy efficacy. Additionally, we present explanations for key Cy side effects related to the nature and site of its bioactivation. Finally, we discuss the role of busulphan in conditioning regimens in the Cy metabolic pathway as a clinical example of drug‐drug interactions involving several enzymes. By the end of this article, our aim is to have provided a comprehensive summary of Cy pharmacogenomics and the effect on its kinetics. The utility of these findings in the development of new strategies for Cy personalized patient dose adjustment will aid in the future optimization of patient specific Cy dosages and ultimately in improving clinical outcomes. In conclusion, CYP2B6 and several other enzyme polymorphisms can alter Cy kinetics and consequently the clinical outcomes. However, the precise quantification of Cy kinetics in any individual patient is complex as it is clearly under multifactorial genetic control. Additionally, other clinical factors such as the patient’s age, diagnosis, concomitant medications, and clinical status should also be considered.

Cyclophosphamide (Cy) is a prodrug that is mainly bioactivated by the cytochrome enzyme CYP2B6. Several other enzymes are also involved in its bioactivation and affect its kinetics. Previous studies have shown the effect of the enzymes’ genetic polymorphisms on Cy kinetics and its clinical outcome. These results were controversial primarily because of the involvement of several interacting enzymes in the Cy metabolic pathway, which can be also affected by several clinical factors as well as other drugs interactions. In this article, we present the effect of CYP2B6 polymorphisms on Cy kinetics since it is the main bioactivating enzyme, as well as discussing all previously reported enzymes and clinical factors that can alter Cy efficacy. Additionally, we present explanations for key Cy side effects due to its extrahepatic bioactivation. Finally, we discuss the role of busulphan in conditioning regimens in the Cy metabolic pathway as a clinical example of drug-drug interactions involving several enzymes. By the end of this article, our aim is to have provided a conclusive summary of Cy pharmacogenomics and the effect of its kinetics. The use of these findings in new strategies for Cy personalized patient dose adjustment will certainly help in optimizing the Cy dose and in improving the clinical outcome.

New therapeutic options for patients with ovarian cancer are urgently needed. Therefore, we evaluated the efficacy of two second-generation mesothelin (MSLN)-directed CAR T cells in orthotopic mouse models of ovarian cancer. Treatment with CAR T cells expressing an MSLN CAR construct including the CD28 domain (M28z) significantly prolonged survival, but no persistent tumor control was observed. Despite lower response rates, MSLN-4–1BB (MBBz) CAR T cells induced long-term remission in some SKOV3–bearing mice. Tumor-infiltrating M28z and MBBz CAR T cells upregulated PD-1 and LAG3 in an antigen-dependent manner while MSLN+ tumor cells expressed the corresponding ligands (PD-L1 and HLA-DR), demonstrating that coinhibitory pathways impede CAR T-cell persistence in the ovarian tumor microenvironment. Furthermore, profiling plasma soluble factors identified a cluster of M28z- and MBBz-treated mice characterized by elevated T-cell secreted factors that had increased survival, higher CD8+ T-cell tumor infiltration, less exhausted CAR T-cell phenotypes, and increased HLA-DR expression by tumor cells. Altogether, our study demonstrates the therapeutic potential of MSLN-CAR T cells to treat ovarian cancer.Significance:These findings demonstrate that MSLN-directed CAR T cells can provide antitumor immunity against ovarian cancer.