Metabolite Of Cyclophosphamide Research Articles

7770 Damage of Ovarian Vasculature by Chemotherapies induces Ovarian Dysfunction in Mice

Abstract Disclosure: W. So: None. R. Dong: None. Y. Luan: None. A. Abazarikia: None. S. Kim: None. Background: Chemotherapy demonstrates efficacy to destroying cancer cells; however, it can inadvertently impact normal healthy cells, leading to irreversible side effects, particularly affecting the ovaries in female patients. Female cancer survivors encounter endocrine dysfunction and infertility due to ovarian damage caused by gonadotoxic cancer therapies. The ovary, a vital organ responsible for producing oocytes and endocrine hormones, faces significant challenges following such treatment. A study with premenopausal breast cancer patients reported a significant reduction in ovarian blood flow and volume immediately following chemotherapy. The preservation of ovarian function depends on the ovarian vasculature in supporting the development and maintenance of ovarian follicles. Despite its importance, the relationship between ovarian vasculature and follicle following chemotherapy has not been studied. Results: To investigate the direct impacts of chemotherapy, ovaries from postnatal 5 CD-1 mice were subjected to testing with three chemotherapeutic agents: cisplatin (CDDP), cyclophosphamide (CPA), and doxorubicin (DOXO). The expression of CD31/PECAM-1 (platelet endothelial adhesion molecule) exhibited a significant decrase after 96 hours of culture with 4-HC, an active metabolite of CPA. This reduction implies that ovarian vasculature was also compromised when chemotherapy eliminated immature follicles. In order to evaluate the influence of vascular endothelial growth factor (VEGF) in safeguarding both vasculature and ovarian follicles, ovaries were co-cultured with VEGF165 or VEGF165b in combination with chemotherapy. Interestingly, pre-treatment with VEGF165 before 4-HC led to an increased expression of CD31 in the cortex area, while VEGF165b further diminished CD31 expression compared to treatment with 4-HC alone. Additionally, adolescent CD-1 mice were intraperitoneally injected with CDDP, CPA, or DOXO, and ovaries were harvested one week after injection. Ovaries treated with chemotherapeutic agents exhibited a reduction in ovary weight and decreased CD31 expression compared to control mice. Conclusions: We propose that these chemotherapeutic agents not only induced the loss of ovarian follicles but also affected ovarian vasculature in mice. This suggests a potential decrease in folliculogenesis within the ovary, coupled with the depletion of ovarian reserve, as the delivery of nutrients and oxygen to growing ovarian follicles may be compromised. VEGF165 may play a beneficial role in maintaining ovarian function by safeguarding ovarian vasculature following chemotherapy. Understanding these intricate dynamics is essential for developing strategies to mitigate the negative impact of cancer therapies on reproductive health in female cancer survivors, particularly in preserving endocrine function and reproductive lifespan. Presentation: 6/2/2024

Pharmacogenomic associations of cyclophosphamide pharmacokinetic candidate genes with 4hydroxycyclophosphamide formation in children with Cancer.

4-hydroxycyclophosphamide (4HCY) is the principal precursor to the cytotoxic metabolite of cyclophosphamide (CY), which is often used as first-line treatment of children with cancer. There is conflicting data regarding the relationship between CY efficacy, toxicity, and pharmacokinetics with the genes encoding proteins involved in 4HCY pharmacokinetics, specifically its formation and elimination. We evaluated germline pharmacogenetics in children with various malignancies receiving their first CY dose. Using linear regression, we analyzed the associations between two pharmacokinetic outcomes - how fast a child cleared CY (i.e., CY clearance) and the ratio of the 4HCY/CY exposure, specifically area under the plasma concentration-time curve (AUC), and 372 single nucleotide polymorphisms (SNP) in 14 drug-metabolizing transporters or enzymes involved in 4HCY formation or elimination. Age was associated with the ratio of 4HCY/CY AUC (P = 0.004); Chemotherapy regimen was associated with CY clearance (P = 0.003). No SNPs were associated with CY clearance or the ratio of 4HCY/CY AUC after controlling for a false discovery rate. Age and chemotherapy regimen, but not germline pharmacogenomics, were associated with CY clearance or the ratio of 4HCY/CY AUC. Other methods, such as metabolomics or lipidomics, should be explored.

The role of declining ataxia-telangiectasia-mutated (ATM) function in oocyte aging

Despite the advances in the understanding of reproductive physiology, the mechanisms underlying ovarian aging are still not deciphered. Recent research found an association between impaired ATM-mediated DNA double-strand break (DSB) repair mechanisms and oocyte aging. However, direct evidence connecting ATM-mediated pathway function decline and impaired oocyte quality is lacking. The objective of this study was to determine the role of ATM-mediated DNA DSB repair in the maintenance of oocyte quality in a mouse oocyte knockdown model. Gene interference, in vitro culture, parthenogenesis coupled with genotoxicity assay approaches, as well as molecular cytogenetic analyses based upon next-generation sequencing, were used to test the hypothesis that intact ATM function is critical in the maintenance of oocyte quality. We found that ATM knockdown impaired oocyte quality, resulting in poor embryo development. ATM knockdown significantly lowered or blocked the progression of meiosis in vitro, as well as retarding and reducing embryo cleavage after parthenogenesis. After ATM knockdown, all embryos were of poor quality, and none reached the blastocyst stage. ATM knockdown was also associated with an increased aneuploidy rate compared to controls. Finally, ATM knockdown increased the sensitivity of the oocytes to a genotoxic active metabolite of cyclophosphamide, with increased formation of DNA DSBs, reduced survival, and earlier apoptotic death compared to controls. These findings suggest a key role for ATM in maintaining oocyte quality and resistance to genotoxic stress, and that the previously observed age-induced decline in oocyte ATM function may be a prime factor contributing to oocyte aging.

Anti-Mullerian hormone attenuates both cyclophosphamide-induced damage and PI3K signalling activation, while rapamycin attenuates only PI3K signalling activation, in human ovarian cortex in vitro.

What are the effects of cyclophosphamide exposure on the human ovary and can anti-Mullerian hormone (AMH) and rapamycin protect against these? Exposure to cyclophosphamide compromises the health of primordial and transitional follicles in the human ovarian cortex and upregulates PI3K signalling, indicating both direct damage and increased follicular activation; AMH attenuates both of these chemotherapy-induced effects, while rapamycin attenuates only PI3K signalling upregulation. Studies primarily in rodents demonstrate that cyclophosphamide causes direct damage to primordial follicles or that the primordial follicle pool is depleted primarily through excessive initiation of follicle growth. This increased follicular activation is mediated via upregulated PI3K signalling and/or reduced local levels of AMH production due to lost growing follicles. Furthermore, while rodent data show promise regarding the potential benefits of inhibitors/protectants alongside chemotherapy treatment to preserve female fertility, there is no information about the potential for this in humans. Fresh ovarian cortical biopsies were obtained from 17 healthy women aged 21-41 years (mean ± SD: 31.8 ± 4.9 years) at elective caesarean section. Biopsies were cut into small fragments and cultured for 24 h with either vehicle alone (DMSO), the active cyclophosphamide metabolite 4-hydroperoxycyclophosphamide (4-HC) alone, 4-HC + rapamycin or 4-HC+AMH. Two doses of 4-HC were investigated, 0.2 and 2 μM in separate experiments, using biopsies from seven women (aged 27-41) and six women (aged 21-34), respectively. Biopsies from four women (aged 28-38) were used to investigate the effect of rapamycin or AMH only. Histological analysis of ovarian tissue was undertaken for follicle staging and health assessment. Western blotting and immunostaining were used to assess activation of PI3K signalling by measuring phosphorylation of AKT and phosphorylated FOXO3A staining intensity, respectively. Exposure to either dose of 4-HC caused an increase in the proportion of unhealthy primordial (P < 0.0001, both doses) and transitional follicles (P < 0.01 for low dose and P < 0.01 for high dose) compared to vehicle. AMH significantly reduced follicle damage by approximately half in both of the investigated doses of 4-HC (P < 0.0001), while rapamycin had no protective effect on the health of the follicles. Culture with AMH or rapamycin alone had no effect on follicle health. Activation of PI3K signalling following 4-HC exposure was demonstrated by both Western blotting data showing that 4-HC increased in AKT phosphorylation and immunostaining showing increased phosphorylated FOXO3A staining of non-growing oocytes. Treatment with rapamycin reduced the activation of PI3K signalling in experiments with low doses of 4-HC while culture with AMH reduced PI3K activation (both AKT phosphorylation and phosphorylated FOXO3A staining intensity) across both doses investigated. These in vitro studies may not replicate in vivo exposures. Furthermore, longer experiment durations are needed to determine whether the effects observed translate into irreparable deficits of ovarian follicles. These data provide a solid foundation on which to explore the efficacy of AMH in protecting non-growing ovarian follicles from gonadotoxic chemotherapies. Future work will require consideration of the sustained effects of chemotherapy treatment and potential protectants to ensure these agents do not impair the developmental competence of oocytes or lead to the survival of oocytes with accumulated DNA damage, which could have adverse consequences for potential offspring. This work was supported by grants from TENOVUS Scotland, the Academy of Medical Sciences (to R.R.), the Medical Research Council (G1100357 to R.A.A., MR/N022556/1 to the MRC Centre for Reproductive Health), and Merck Serono UK (to R.A.A.). R.R., H.L.S., N.S., and E.E.T. declare no conflicts of interest. R.A.A. reports grants and personal fees from Roche Diagnostics and Ferring Pharmaceuticals, and personal fees from IBSA and Merck outside the submitted work. N/A.

Mechanism-of-Action-Based Development of New Cyclophosphamides

Even more than 60 years after its introduction into the clinic, cyclophosphamide (CP), which belongs to the group of alkylating cytostatics, is indispensable for the treatment of cancer. This is despite the fact that its exact mechanism of action was unknown until a few years ago, and therefore, all attempts to improve the effectiveness of CP failed. The reason for not knowing the mechanism of action was the uncritical transfer of the chemical processes that lead to the formation of the actual alkylating CP metabolite phosphoreamide mustard (PAM) in vitro to in vivo conditions. In vitro—e.g., in cell culture experiments—PAM is formed by β-elimination of acrolein from the pharmacologically active CP metabolite aldophosphamide (ALD). In vivo, on the other hand, it is formed by enzymatic cleavage of ALD by phosphodiesterases (PDE) with the formation of 3-hydroxypropanal (HPA). The discovery of HPA as a cyclophosphamide metabolite, together with the discovery that HPA is a proapoptotic aldehyde and the discovery that the cell death event in therapy with CP is DNA-alkylation-initiated p53-controlled apoptosis, led to the formulation of a mechanism of action of CP and other oxazaphosphorine cytostatics (OX). This mechanism of action is presented here and is confirmed by newly developed CP-like compounds with lower toxicity and an order of magnitude better effectiveness.

Abstract 5984: CDK9 inhibition as a potential therapeutic strategy in Ewing sarcoma

Abstract Ewing sarcoma (EWS) is the second most common bone and soft tissue sarcoma in children and adolescents and accounts for approximately 2% of all childhood cancer diagnoses. EWS is a highly aggressive cancer: the overall 5-year survival rate for localized and metastatic EWS are 67 and 38%, respectively. Each year, approximately 200 children and adolescents in the United States are diagnosed with EWS. Genetically, nearly all EWS have chromosomal translocations in which a member of the FET gene family is fused with an ETS transcription factor, with 85% of cases being EWSR1-FLI1. Cyclin-dependent kinase 9 (CDK9) is a serine/threonine protein kinase involved in transcription elongation through phosphorylation and activation of RNA polymerase II (RPB1) and increases the levels of key oncogenic genes like myeloid cell leukemia-1 (MCL-1) and c-Myc, which are reported to be involved in chemoresistance. CDK9 may be a viable target in transcriptionally addicted cancers including EWS driven by oncogenic fusion genes like EWSR1-FLI1. TP-1287 is an investigational orally delivered phosphate pro-drug of alvocidib, a potent CDK9 inhibitor. We hypothesized that alvocidib, the pharmaceutically active form of TP-1287, may show activity in EWS cells as a single agent and in combination with standard of care agents. Alvocidib demonstrated the suppression of downstream targets of CDK9 including c-Myc in EWS cell lines after 6-hr treatment. In cell viability assays using CellTiter-Glo, alvocidib resulted in IC50 values of 68 - 125 nM in EWS cell lines after 3-day treatment and 27 - 160 nM in EWS cells from patient derived xenograft (PDX) models, after 6-day treatment. MCL-1 amplified EWS cells were observed significantly more sensitive to alvocidib than MCL-1 diploid EWS cells in the EWS cells from PDX models (p=0.004). Further bioinformatic analysis to predict alvocidib sensitivity is currently underway. Alvocidib demonstrated an additive inhibitory response in combination with topotecan, phosphoramide mustard, a biologically active metabolite of cyclophosphamide, and palifosfamide, a biologically active metabolite of ifosfamide, in EWS cell lines after 3-day treatment. Alvocidib treatment showed reduction of RAD51 which is involved in DNA damage response (DDR), suggesting the activity of alvocidib on DDR may contribute to this additive response. In an in vivo preclinical study using the A-673 model, TP-1287 (2.5 mg/kg, QD) showed tumor growth inhibition (TGI). In vivo combination studies with standard of care agents using EWS xenograft models are currently ongoing. In summary, alvocidib has shown activity inhibiting the growth of EWS cells as a single agent and an additive response in combination with EWS standard of care agents in EWS cell lines. TP-1287 may be a potential therapeutic option for the current regimen in EWS. TP-1287 is being investigated for solid tumors including EWS (clinicaltrials.gov, NCT03604783). Citation Format: Yuta Matsumura, Richard E. Heinz, Curtis A. Allred, Adam Siddiqui, Jason M. Foulks, Steven L. Warner. CDK9 inhibition as a potential therapeutic strategy in Ewing sarcoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5984.

206 - Anaphylaxis to Cyclophosphamide Metabolites during Lymphodepletion for CAR-T Therapy

206 - Anaphylaxis to Cyclophosphamide Metabolites during Lymphodepletion for CAR-T Therapy

OR06-1 Cyclophosphamide Depletes Primordial Follicles via the p63 Apoptotic Pathway

Abstract Cancer therapies often cause serious side effects, affecting the quality of life for cancer survivors. The ovary can be affected by cancer therapies, causing premature ovarian insufficiency, leading to endocrine dysfunction and infertility. Thus, maintaining ovarian function against cancer treatment is an unmet need for female cancer patients. Cyclophosphamide (CPA), a common chemotherapeutic agent, is metabolized in vivo and forms DNA crosslinks, inducing apoptosis in rapidly proliferating tumor cells. However, the underlying mechanism of the CPA-induced oocyte death in ovarian reserve remains unclear. This study aims to investigate the mechanism of oocyte death in primordial follicles by generating oocyte-specific Abl1 and p63 knockout and Pik3ca* knockin mouse models using Gdf9-iCre+. Postnatal day 7 female mice were i.p. injected w/wo CPA. Notably, we found CPA drastically reduced the number of primordial follicles without increasing the number of growing follicles. The quantification of surviving follicles validated that 90% of the primordial follicles from oocyte-specific Abl1 knockout mice were lost following CPA treatment in vivo and in vitro. Concurrently, high expression of CHK2 was detected in the oocytes of the ovary cultured with CPA metabolite in vitro. This implied CHK2 rather than ABL is a possible tyrosine kinase for CPA-induced oocyte death. Most of all, p63 was a key player for CPA-induced oocyte death, supported by the result that p63 knockout oocytes were rescued after CPA treatment. To clarify whether the ovaries lose follicles via activation or apoptosis pathway, PIK3CA* mice were examined with CPA. As expected, primordial follicles and primordial follicles with activated oocytes in the ovary of PIK3CA* mice survived against CPA due to constitutive PI3K activity in them. This indicates activated follicles resist gonadotoxic reagents, although p63 is expressed inside their oocytes. Accordingly, the apoptosis markers, BAX and cleaved PARP were highly induced with CPA injection in a time-dependent manner in the ovaries from wild-type female mice but not from the p63 knockout. The double-strand break also occurred in the nucleus of oocytes post CPA administration as γH2AX was detected. Interestingly, OPA1, a protein required for mitochondrial fusion, was highly induced inside the oocyte cytoplasm of p63 knockout, while oocytes in wild-type mice time-dependently lost the OPA1 expression by CPA treatment. This indicates that oocytes without p63 in the nucleus survive and induce mitochondrial fusion to escape apoptosis by mitochondrial damages. In conclusion, CPA induces depletion of oocytes of primordial follicles through the CHK2-TAp63 apoptotic pathway. Presentation: Saturday, June 11, 2022 11:30 a.m. - 11:45 a.m.

Environmental degradation of human metabolites of cyclophosphamide leads to toxic and non-biodegradable transformation products

The present study assessed the ready biodegradability of the prodrug cyclophosphamide (CPA) and its stable human metabolites in the closed bottle test (CBT). The results of the CBT showed that only the main human metabolite, carboxyphosphamide (CXP), was biodegradable to a certain extent (23 ± 2.4 % ThODNH3). All other metabolites showed neither biodegradation under these conditions nor were any toxic effects on the inoculum observed. Yet, HRMSn results revealed partial primary elimination of all human metabolites and formation of 25 new transformation products. Abiotic degradation via SNi and SN2 reactions was proposed as the main degradation pathway during the CBT. The main degradation products were assigned as 3-(2-chloroethyl)oxazolidin-2-one (COAZ), cytotoxic N-2-chloroethylaziridine (CEZ) and nor‑nitrogen mustard (NNM), an analogue of the chemical warfare agent HN2. While the acute ecotoxicity of the detected products is widely unknown, many have already been reported in medical literature to be either mutagenic, genotoxic, cytotoxic or carcinogenic and may therefore cause a greater risk than their precursors. QSAR models predicted that 16 of them are mutagenic and genotoxic, thus classifying the majority of the chemicals as potential environmental hazards. The central intermediates during the degradation process were proposed as CEZ and its corresponding aziridinium ion. However, other degradation products may occur depending on the type and strength of nucleophiles present in the matrices. Overall, the results demonstrated the importance to include human metabolites in the evaluation of the environmental fate of pharmaceuticals and their risk assessment especially when investigating prodrugs. The results underline the importance of identifying possible degradation products of metabolites, as they can be more toxic than related parent compounds and metabolites and can cause a greater risk to the environment and humans.

Comparison of Dose Adjustment Strategies for Obesity in High-dose Cyclophosphamide Among Adult Hematopoietic Cell Transplantation Recipients: Pharmacokinetic Analysis

Cyclophosphamide (CY) is an alkylating agent widely used in the field of oncology and hematopoietic cell transplantation (HCT). It is recommended to use an adjusted body weight with an adjustment factor of 0.25 (ABW25) for dosing of CY in obese patients undergoing HCT. However, evidence based on the pharmacokinetics (PK) of CY to support this recommendation is lacking. We aimed to identify a dosing strategy of CY that achieves equivalent exposures among obese and nonobese patients. The present study is a secondary analysis of a previously conducted observational PK study of phosphoramide mustard (PM), the final cytotoxic metabolite of CY. Data were collected from 85 adults with hematologic malignancy who received a single infusion of CY 50 mg/kg, fludarabine, ± anti-thymocyte globulin, and a single fraction of total body irradiation as HCT conditioning therapy. A previously developed population PK model in these patients was used for simulations. Using individualized PK parameters from that analysis, simulations were performed to assess cumulative exposures of PM (i.e., area-under-the-curve [AUC]) resulting from 8 different dosing strategies according to various measures of body size: (1) “mg/kg” by total body weight (TBW); (2) “mg/kg” by ideal body weight (IBW); (3) “mg/kg” by fat free mass; (4) “mg/m2” by body surface area (BSA); (5) “mg/kg” by TBW combined with ABW25 (TBW-ABW25); (6) “mg/kg” by IBW combined with ABW25 (IBW-ABW25); (7) “mg/kg” by TBW combined with ABW by adjustment factor of 0.50 (TBW-ABW50); and (8) “mg” by fixed-dose. We defined equivalent exposure as the effect of obesity on PM AUC within ±20% from the PM AUC in the nonobese group, where obesity is defined based on TBW/IBW ratio (i.e., nonobese, <1.2; mildly obese, 1.2-1.5; and moderately/severely obese, >1.5). Primary and secondary outcomes were PM AUC0-8hours and PM AUC0-infinity, respectively. In the 85 patients, with the median age of 63 years (range 21-75), 46% were classified as mildly and 25% were moderately/severely obese based on the TBW/IBW ratio. Negative correlations (i.e., higher the extent of obesity, lower the PM AUC) were shown when dosing simulations were based on IBW, TBW-ABW25, and fixed dosing (P < .05). Positive correlations were shown when dosing was simulated by TBW (P < .05). None of the 8 dosing strategies attained equivalent PM AUC0-8hours between patients with versus without obesity, whereas dosing by BSA and TBW-ABW50 attained equivalent PM AUC0-infinity (P < .05). Our study predicted that the recommended ABW25 dose adjustment may result in lower exposure of CY therapy in obese patients than in nonobese. A CY dosing strategy that would result in similar PM concentrations between obese and nonobese was not identified for early exposure (i.e., PM AUC0-8hours). The data suggest though that CY dosing based on “mg/m2” by BSA or “mg/kg” by TBW-ABW50 would result in similar total exposure (i.e., PM AUC0-infinity) and may minimize exposure differences in obese and nonobese patients.

Association between gene polymorphisms in the cyclophosphamide metabolism pathway with complications after haploidentical hematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for patients with hematologic malignances. Haploidentical HSCT (Haplo-HSCT) is an alternative option for patients who do not have an HLA-matched donor. The use of post-transplantation high dose cyclophosphamide (PT-Cy) is commonly employed for graft-versus-host disease (GVHD) prophylaxis in haplo-HSCT. Cyclophosphamide (Cy) is an alkylating agent with antineoplastic and immunosuppressive activity, whose bioactivation requires the activity of polymorphic enzymes in the liver to produce phosphoramide mustard, which is a DNA alkylating agent. To identify polymorphisms in the genes of Cy metabolism and correlate them with post-HSCT complications [GVHD, sinusoidal obstruction syndrome (SOS), hemorrhagic cystitis (HC) and transplant-related mortality (TRM)], we designed a custom next-generation sequencing panel with Cy metabolism enzymes. We analyzed 182 patients treated with haplo-HSCT with PT-Cy from 2007 to 2019, detecting 40 variants in 11 Cy metabolism genes. Polymorphisms in CYP2B6, a major enzyme involved in Cy activation, were associated with decreased activity of this enzyme and a higher risk of Graf-versus-host disease (GVHD). Variants in other activation enzymes (CYP2A6, CYP2C8, CYP2C9, CYP2C19) lead to decreased enzyme activity and were associated with GVHD. Polymorphisms in detoxification genes such as glutathione S-transferases decreased the ability to detoxify cyclophosphamide metabolites due to lower enzyme activity, which leads to increased amounts of toxic metabolites and the development of III-IV acute GVHD. GSMT1*0 a single nucleotide polymorphism previously recognized as a risk factor for SOS was associated with a higher risk of SOS. We conclude that polymorphisms of genes involved in the metabolism of cyclophosphamide in our series are associated with severe grades of GVHD and toxicities (SOS and TRM) after haplo-HSCT and could be used to improve the clinical management of transplanted patients.

Fractionated oral dosing and its effect on cyclophosphamide pharmacokinetics in dogs with high-grade multicentric lymphoma.

Cyclophosphamide (CP) is an alkylating agent commonly included in multi-drug treatment protocols for canine cancer. As a prodrug, CP requires hepatic metabolism for activation to the intermediate compound 4-hydroxycyclophosphamide (4-OHCP) which then spontaneously forms alkylating phosphoramide mustard. CP is frequently administered in a fractionated manner, with the total dose given over multiple days. CP is reported to cause auto-induction of metabolism in humans, with faster CP clearance and relatively increased 4-OHCP formation following fractionated versus bolus dosing, however canine pharmacokinetic studies of CP dose fractionation are lacking. The study objective was to evaluate the pharmacokinetics of fractionated oral CP dosing at a dose of 200-250 mg/m2 over 3 to 4 days in a prospectively identified population of cancer-bearing dogs. Plasma concentrations of CP and 4-OHCP were measured by ultra-high performance liquid chromatography tandem-mass spectrometry in eight dogs following the first and last doses to assess for auto-induction of CP metabolism. No significant difference in the rate of CP elimination between first and last doses were detected (0.73 ± 0.46 vs. 1.22 ± 0.5h-1 ; p=.125). Additionally, no significant difference in dose-normalized 4-OHCP exposure was identified between first and last doses (5.9 ± 2.1 vs. 7.9 ± 6.4h × ng/ml; p=.936). These results suggest that fractionated dosing may not increase exposure to the active metabolite of CP in dogs as it does in humans. As such, standard bolus dosing and fractionated dosing may be equivalent in terms of bio-activation of CP in dogs administered a dose of 200-250 mg/m2 .

Post-transplant cyclophosphamide pharmacokinetics and haploidentical hematopoietic cell transplantation outcomes: an exploratory study

Pharmacokinetics of cyclophosphamide has been explored to optimize conditioning dosing. We hypothesized that post-transplant cyclophosphamide (PTCy) metabolite carboxy-ethyl phosphoramide mustard (CEPM) pharmacokinetics might impact haploidentical transplantation (haplo-HCT) outcomes. CEPM area under the curve (AUC0–48) was determined by eleven sampling timepoints on day +3/+4 using LC-MS/MS. The median CEPM AUC0–48 in a cohort of 30 patients was 14.2 (14) mg·hr/L. The incidence of severe chronic graft-versus-host disease (GVHD) (73% vs. 11%, p = 0.02), and GVHD-/relapse-free survival (GRFS) was significantly inferior in the CEPM AUC0–48 < 14 mg·hr/L group (54 days vs. 344 days, p = 0.02). There was, however, no difference in grade III-IV acute GVHD (38% vs. 14%, p = 0.12) and overall survival (295 days vs. not reached, p = 0.2). CEPM AUC0–48, is associated with severe chronic GVHD and GRFS post-haplo-HCT in this exploratory study. There is scope for personalizing day + 4 PTCy dose based on day + 3 CEPM AUC0–8.

Quantification of N, N’ N’’-triethylenethiophosphoramide, N, N’ N’’-triethylenephosphoramide, cyclophosphamide, and 4-hydroxy-cyclophosphamide in microvolume human plasma to support neonatal and pediatric drug studies

N, N’ N’’-triethylenethiophosphoramide (thiotepa) and cyclophosphamide (CP) are alkylating agents used for a variety of malignant and non-malignant disorders. Both drugs are metabolized by cytochrome P450 enzymes to form active metabolites. To support pharmacokinetic studies of thiotepa and CP in children, we sought to develop assays to determine parent drug and metabolite concentration in small volume plasma samples. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for assay development. CP metabolite 4-hydroxycyclophosphamide (4OHCP) was converted to the more stable semicarbazone derivative (4OHCP-SCZ) for quantitation. Samples (10 µL) were extracted by solid-phase extraction and injected onto the LC-MS/MS system equipped with a pentafluorophenyl reverse phase column (2.1 × 50 mm, 2.7 µm). Electrospray ionization in positive mode was used for detection. Multiple reaction monitoring of the precursor-to-product ion transitions m/z 190→147 for thiotepa, 174→131 for tepa, 261→233 for CP, and 334→221 for 4OHCP-SCZ was selected for quantification. The ion transitions m/z 202→155 for thiotepa-d12, 186→139 for tepa-d12, 267→237 for CP-d4, and 340→114 for 4OHCP-d4-SCZ were selected for the internal standard (IS) corresponding to each analyte. The less abundant IS ions from 37Cl were used for CP-d4 and 4OHCP-d4-SCZ to overcome the cross-talk interference from the analytes. Under optimized conditions, retention times were 0.67 min for tepa and its IS, 2.50 min for thiotepa and its IS, 2.52 min for 4OHCP-SCZ and its IS, and 2.86 min for CP and its IS. Total run time was 5 min per sample. The calibration ranges were 2.5-2,000ng/mL for thiotepa and tepa, 20-10,000ng/mL for CP and 20-5,000 ng/mL for 4OHCP; Dilution integrity for samples above the calibration range was validated with 10-fold dilution for thiotepa/tepa and 20-fold dilution for CP/4OHCP . Recoveries ranged from 86.3-93.4% for thiotepa, 86.3-89.0% for tepa, 90.2-107% for CP, and 99.3-115% for 4OHCP-SCZ. The IS normalized matrix effect was within (100±7) % for all 4 analytes. Plasma samples at room temperature were stable for at least 60 hours for thiotepa, 6 days for tepa, and 24 hours for CP and 4OHCP-SCZ. Plasma samples for thiotepa/tepa were stable after 4 freeze-thaw cycles, and for CP/4OHCP-SCZ were stable after 3 freeze-thaw cycles. The assays were validated and applied to clinical studies requiring small sample volumes.

Protective effects of a SIRT1 inhibitor on primordial follicle activation and growth induced by cyclophosphamide: insights from a bovine in vitro folliculogenesis system

PurposeAlthough oncological advances have improved survival rates of female cancer patients, they often suffer a reduced fertility due to treatment side effects. In the present study, we evaluated the potential fertoprotective effects of the specific inhibitor of SIRT1, EX-527, on the gonadotoxic action exerted by cyclophosphamide (CPM) on loss of primordial follicles (PFs).MethodsThe effects of the CPM metabolite phosphoramide mustard (PM) on follicle activation, growth and viability and the protective action of EX-527 against PM effects were evaluated on bovine ovarian cortical strips in vitro cultured for 1 or 6 days. To understand whether PFs exposed to PM plus EX-527 were able to activate and grow to the secondary stage after suspension of the treatment, strips cultured for 3 days in PM plus EX-527 for 3 days were transferred to plain medium until day 6. Follicle growth and health were evaluated through histology and viability assay at a confocal microscope. In order to investigate the molecular pathways underlying the ovarian response to PM in the presence of EX-527, we analysed the protein level of SIRT1, HuR, PARP1 and SOD2 after 1 day of in vitro culture.ResultsWe found that (1) PM, the main CPM active metabolite, promotes PF activation; (2) the ovarian stress response induced by PM includes a SIRT1-dependent pathway; and (3) EX-527 reduces PF activation and growth induced by PM.ConclusionSIRT1 can represent a candidate molecule to be targeted to protect ovarian follicles from alkylating agents and EX-527 could represent a potential fertoprotective agent for cancer patients.

Abstract P4-10-16: Increased chemotherapy-induced ovarian reserve loss and impaired oocyte quality in a mouse ATM knock-down model: An augury for women with ATM-pathway-pathogenic-variants-associated breast cancer?

Abstract Rationale: Breast cancer chemotherapy commonly causes the depletion of ovarian primordial follicle reserve, which results in premature ovarian insufficiency and infertility. It is critical to understand the mechanism of this ovarian damage to be able to develop pharmacological fertility preservation methods. We have previously shown that the main mechanism of ovarian follicle loss induced by cyclophosphamide (C) and doxorubicin (A) is via the induction of double-strand DNA breaks (DSBs) and the resulting apoptotic death of primordial follicles. We have also shown that some oocytes may repair this damage by activating the ATM-mediated DNA DSB repair pathway (ATM-Pathway). We have also demonstrated that the oocytes of women with BRCA1 pathogenic variants are more prone to DNA damage and such women are more likely to lose ovarian reserve after AC-based chemotherapy. BRCA1 is a key member of the ATM-Pathway. An increasing number of women are diagnosed with breast cancer associated with mutations of the other members of the ATM-Pathway. This includes ATM, which is the orchestrator of the ATM-Pathway. Therefore, we hypothesized that ATM-deficient oocytes may be more prone to chemotherapy-induced damage. In addition, given our recent findings of the role of declining BRCA1 function in oocyte aging, we hypothesized that ATM function is important in oocyte and embryo quality. Having both increased liability to chemotherapy-induced loss and accelerated ovarian aging can be a double-whammy for women with breast cancer that are associated with the pathogenic variants of the ATM-Pathway genes. Methods: Germinal Vesicle (GV) stage oocytes were collected from 6-wk old mice 48h after ovarian stimulation. Oocytes were then microinjected with 50uM ATM small interfering RNA (siRNA). The scrambled-siRNA-injected and un-injected oocytes served as negative controls. In separate experiments, effective ATM-knockdown (~70%) was confirmed by single-cell real-time-qPCR. Then, oocytes were subjected to subsequent in vitro maturation followed by parthenogenesis or 4h exposure to the active metabolite of cyclophosphamide, 4-hydroperoxycyclophosphamide (4-HC, 20µg/mL). Experiments were repeated ≥ thrice. One-way ANOVA and non-parametric Kruskal-Wallis posthoc tests were used for statistical analysis.Results: ATM-knockdown resulted in a significant reduction of oocyte maturation compared with scrambled or uninjected (29%, n=157 vs. 78%, n=172 vs. 84%, n=151) (p&amp;lt;0.001 siATM vs. the controls), suggesting altered oocyte quality. The siATM parthenotes had lower cleavage and blastocyst rates (15% and 0%, n=20,) compared with scrambled (63% and 18%, n=22), and uninjected controls (66% and 24%, n=21) (p&amp;lt;0.05 compared to either control), and demonstrated impaired morphology. Moreover, ATM-knock-down resulted in increased oocyte sensitivity to chemotherapy; with significantly lower survival rates (15%, n=37) compared to scrambled (55%, n=48) or un-injected controls (57% n=48; p&amp;lt;0.001) after the 4-HC exposure. Conclusions: This mouse model indicates that intact ATM function is critical in both oocyte resistance against chemotherapy and the maintenance of egg and embryo quality. Clinical studies are justified to determine if women with ATM pathogenic variants have impaired egg and embryo quality and are more prone to chemotherapy-induced loss of ovarian reserve and fertility. Citation Format: Kutluk H Oktay, Xiu Tan, Katarzyna Szymanska-Vandendriessche. Increased chemotherapy-induced ovarian reserve loss and impaired oocyte quality in a mouse ATM knock-down model: An augury for women with ATM-pathway-pathogenic-variants-associated breast cancer? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-10-16.

Cardiotoxicity of cyclophosphamide's metabolites: an in vitro metabolomics approach in AC16 human cardiomyocytes.

Cyclophosphamide is a widely used anticancer and immunosuppressive prodrug that unfortunately causes severe adverse effects, including cardiotoxicity. Although the exact cardiotoxic mechanisms are not completely understood, a link between cyclophosphamide's pharmacologically active metabolites, namely 4-hydroxycyclophosphamide and acrolein, and the toxicity observed after the administration of high doses of the prodrug is likely. Therefore, the objective of this study is to shed light on the cardiotoxic mechanisms of cyclophosphamide and its main biotransformation products, through classic and metabolomics studies. Human cardiac proliferative and differentiated AC16 cells were exposed to several concentrations of the three compounds, determining their basic cytotoxic profile and preparing the next study, using subtoxic and toxic concentrations for morphological and biochemical studies. Finally, metabolomics studies were applied to cardiac cells exposed to subtoxic concentrations of the aforementioned compounds to determine early markers of damage. The cytotoxicity, morphological and biochemical assays showed that 4-hydroxycyclophosphamide and acrolein induced marked cardiotoxicity at µM concentrations (lower than 5µM), being significantly lower than the ones observed for cyclophosphamide (higher than 2500μM). Acrolein led to increased levels of ATP and total glutathione on proliferative cells at 25µM, while no meaningful changes were observed in differentiated cells. Higher levels of carbohydrates and decreased levels of fatty acids and monoacylglycerols indicated a metabolic cardiac shift after exposure to cyclophosphamide's metabolites, as well as a compromise of precursor aminoacids used in the synthesis of glutathione, seen in proliferative cells' metabolome. Overall, differences in cytotoxic mechanisms were observed for the two different cellular states used and for the three molecules, which should be taken into consideration in the study of cyclophosphamide cardiotoxic mechanisms.

Effects of cyclophosphamide related genetic variants on clinical outcomes of adult hematopoietic cell transplant patients.

Genetic variants may influence the pharmacokinetics and pharmacodynamics (PKPD) of cyclophosphamide (CY). CY plays a critical role in conditioning chemotherapy for hematopoietic cell transplantation (HCT), but its use is limited by toxicity. We explored the effect of genetic variants, potentially affecting PKPD of CY, and outcomes after HCT. This observational pharmacogenomic study included 85 adults with hematologic malignancies who received reduced intensity conditioning with CY, fludarabine, and total body irradiation. We collected recipient DNA prior to HCT and evaluated 97 candidate variants in 66 genes and 3 metabolism phenotypes potentially involved in PKPD pathways of CY. In multivariable analysis we investigated the association between the genotypes and four clinical outcomes: Day 180 non-relapse mortality (NRM) and day 180 overall survival (OS), acute graft-versus-host-disease(aGVHD) grades 2-4, and engraftment. p values were not adjusted for multiple testing. The median recipient age was 63years (range 21-75). Acute myeloid leukemia was the most common diagnosis (34%; n = 29). In multivariable analysis adjusted for exposure to phosphoramide mustard, the final active metabolite of CY, we identified 6 variants in 6 genes associated with at least one of theclinical outcomes. An ABCC4 variant (rs9561778) was associated with poor Day 180 NRM (p < 0.01), MUTYH variant (rs3219484) with higher Day 180 NRM and aGVHD (both p < 0.01), and SYNE1 variant (rs4331993) with better Day 180 OS and engraftment (both p ≤ 0.01). The present study suggests that genetic variants influencing the PKPD of CY may help identify patients at risk for inferior outcomes after HCT using CY-based reduced-intensity conditioning.

Peroxisome proliferator-activated receptor-γ signalling protects hair follicle stem cells from chemotherapy-induced apoptosis and epithelial-mesenchymal transition.

Permanent chemotherapy-induced alopecia (pCIA), for which preventive interventions remain limited, can manifest with scarring. While the underlying pathomechanisms of pCIA are unclear, depletion of epithelial hair follicle (HF) stem cells (eHFSCs) is likely to play a role. To explore the hypothesis that, besides apoptosis, eHFSCs undergo pathological epithelial-mesenchymal transition (EMT) in pCIA, thus explaining the scarring phenotype. Furthermore, we tested whether a peroxisome proliferator-activated receptor (PPAR)-γ modulator could prevent pCIA-associated pathomechanisms. Organ-cultured human scalp HFs were treated with the cyclophosphamide metabolite 4-hydroperoxycyclophosphamide (4-HC). Additionally, HFs were pretreated with the agonistic PPAR-γ modulator N-acetyl-GED-0507-34-Levo (NAGED), which has previously been shown to promote K15 expression and antagonize EMT in eHFSCs. In accordance with anticipated hair bulb cytotoxicity, dystrophy and catagen induction, 4-HC promoted apoptosis along with increased p53 expression, DNA damage and pathological EMT in keratin 15+ (K15) eHFSCs, as evidenced by decreased E-cadherin expression and the appearance of fibronectin+ and vimentin+ cells in the hair bulge. Pretreatment with NAGED protected against 4-HC-induced hair bulb cytotoxicity/dystrophy, and apoptosis, p53 upregulation and EMT in the bulge, thereby significantly preventing depletion of K15+ human eHFSCs ex vivo. Since a key cyclophosphamide metabolite alone suffices to damage and deplete human scalp eHFSCs by promoting apoptosis, DNA damage and EMT ex vivo, strategies to prevent pCIA need to target these pathomechanisms. Given the ability of NAGED to prevent chemotherapy-induced eHFSCs damage exvivo, our study introduces the stimulation of PPAR-γ signalling as a novel intervention strategy for the prevention of pCIA.

Repeated Low-Dose Acrolein Triggers Irreversible Lamina Propria Edema in Urinary Bladder, Transient Voiding Behavior and Widening of Eyes to Mechanical Stimuli

Acrolein is a metabolite of cyclophosphamide (CYP), an alkylating agent used for a wide range of benign and malignant diseases. CYP treatments are known to trigger hemorrhagic cystitis in patients and animals. Significant effort has been made to prevent CYP/acrolein-induced cystitis, while still maintaining its therapeutic benefits. As a result, supplementary therapeutic options to mediate the protective role against CYP/acrolein and lower doses of CYP are currently given to targeted patients, as compared to past treatments. There is still a need to further study the effects of the repeated low-dose CYP/acrolein on the pathophysiology of the urinary bladder. In our study, a one-time treatment of acrolein and repeated low-dose acrolein triggered the thickening of the smooth muscle and lamina propria in the urinary bladder of C57BL/6J mice, respectively. The first dose of acrolein did not trigger voiding dysfunction, but the second dose triggered high-volume low-frequency voiding. Interestingly, our new scoring criteria and concurrent behavioral assessment revealed that mice with repeated low-dose acrolein had a wider opening of eyes in response to mechanical stimuli. Our study suggests that clinical symptoms among patients undergoing prolonged low-dose CYP may differ from previously reported symptoms of CYP-induced hemorrhagic cystitis.