Reid, Joel M.

AbstractThe purpose of this study was to develop and validate a population pharmacokinetic model for Z‐endoxifen in patients with advanced solid tumors and to identify clinical variables that influence pharmacokinetic parameters. Z‐endoxifen‐HCl was administered orally once a day on a 28‐day cycle (±3 days) over 11 dose levels ranging from 20 to 360 mg. A total of 1256 Z‐endoxifen plasma concentration samples from 80 patients were analyzed using nonlinear mixed‐effects modeling to develop a population pharmacokinetic model for Z‐endoxifen. A 2‐compartment model with oral depot and linear elimination adequately described the data. The estimated apparent total clearance, apparent central volume of distribution, and apparent peripheral volume of distribution were 4.89 L/h, 323 L, and 39.7 L, respectively, with weight‐effect exponents of 0.75, 1, and 1, respectively. This model was used to explore the effects of clinical and demographic variables on Z‐endoxifen pharmacokinetics. Weight, race on clearance, and aspartate aminotransferase on the absorption rate constant were identified as significant covariates in the final model. This novel population pharmacokinetic model provides insight regarding factors that may affect the pharmacokinetics of Z‐endoxifen and may assist in the design of future clinical trials.

Abstract Introduction: Selinexor is a first-in-class, central nervous system (CNS) penetrant, oral inhibitor of exportin 1 (XPO1), the sole nuclear exporter of many key tumor suppressors. Selinexor is FDA-approved for refractory multiple myeloma and DLBCL and has been evaluated in a phase 1 trial in children with leukemia. We report a phase 1 trial of selinexor in children and adolescents with recurrent CNS and solid tumors, including lymphoma (NCT02323880). Methods: A rolling-six design was used to evaluate selinexor (10 or 25 mg tablets) administered twice or once weekly during a 28-day cycle. Dose determination was based on protocol-defined dose limiting toxicity (DLT) using CTCAEv4 during cycle 1. First dose pharmacokinetics (PK) were performed. Results: 43 subjects were enrolled (17 males); median (range) age was 15 (6-20) years. 27 (63%) had CNS tumors, most commonly high-grade glioma (n=12); 16 (37%) had extracranial solid tumors. 42 were evaluable for DLT. At the starting dose (35 mg/m2/dose, twice weekly), no DLTs were observed in 6 subjects, however, 2 subjects had unexpected late myelosuppression delaying initiation of cycle 2. The dosing schedule was amended to twice weekly for 3 weeks followed by a 1 week break. 12 subjects received 35 mg/m2/dose; 4 experienced DLTs [grade 3 fatigue (n=2), grade 3 thrombocytopenia (n=1), or grade 3 ALT increase (n=1)]. The dose was de-escalated to 20 mg/m2/dose, 3 weeks on, 1 week off. 12 subjects enrolled; 3 experienced a DLT [grade 3 increased AST/ALT, acute reversible neurologic changes, or neutropenia (each n=1)]. At the 20 mg/m2 (n=12) and 35 mg/m2 (n=19) dose levels, respectively, the mean ± SD Cmax (ng/ml) was 324±116 and 535±174, and AUC (hr•ng/ml) was 3092 ± 842 and 5156 ± 1227. This was comparable to PK in adults receiving 35 and 50 mg/m2. Based on a desire to achieve a higher Cmax and avoid breaks in schedule, and emerging evidence for similar effectiveness with decreased toxicity in adults receiving continuous once weekly dosing, we evaluated a dosing schedule with once weekly dosing for all 4 weeks of each cycle. At the initial dose level (45 mg/m2 weekly), 2 of 6 subjects had DLTs [prolonged grade 2 thrombocytopenia or grade 3 seizure in a primary CNS tumor patient]. Six subjects received 35 mg/m2/dose once weekly; 1 DLT [grade 3 thrombocytopenia] was observed. Non-dose-limiting toxicity (Grade ≥2 occurring in >10% of subjects during cycle 1) included lymphopenia, leukopenia, neutropenia, thrombocytopenia, anorexia, fatigue, hypophosphatemia, nausea, and vomiting. Subjects received a median (range) of 1 (1-9) cycle; 13 received 2-3 cycles, and 6 received 5-9 cycles. Conclusions: Selinexor-related toxicities were primarily hematological and gastrointestinal. The maximum tolerated dose (MTD) of selinexor in children and adolescents with recurrent solid and CNS tumors is 20 mg/m2/dose twice weekly for 3 weeks followed by one week off. On a continuous once weekly schedule, the MTD and recommended phase 2 starting dose of selinexor is 35 mg/m2/dose. Citation Format: Adam L. Green, Charles G. Minard, Xiaowei Liu, Joel M. Reid, Kerice Pinkney, Stephan Voss, Marvin D. Nelson, Elizabeth Fox, Brenda J. Weigel, Julia Glade Bender. Phase 1 trial of selinexor in children and adolescents with recurrent/refractory solid and CNS tumors (ADVL1414): A Children’s Oncology Group Phase 1 Consortium trial [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P162.

ObjectiveEpalrestat, an aldose reductase inhibitor increases phosphomannomutase (PMM) enzyme activity in a PMM2‐congenital disorders of glycosylation (CDG) worm model. Epalrestat also decreases sorbitol level in diabetic neuropathy. We evaluated the genetic, biochemical, and clinical characteristics, including the Nijmegen Progression CDG Rating Scale (NPCRS), urine polyol levels and fibroblast glycoproteomics in patients with PMM2‐CDG.MethodsWe performed PMM enzyme measurements, multiplexed proteomics, and glycoproteomics in PMM2‐deficient fibroblasts before and after epalrestat treatment. Safety and efficacy of 0.8 mg/kg/day oral epalrestat were studied in a child with PMM2‐CDG for 12 months.ResultsPMM enzyme activity increased post‐epalrestat treatment. Compared with controls, 24% of glycopeptides had reduced abundance in PMM2‐deficient fibroblasts, 46% of which improved upon treatment. Total protein N‐glycosylation improved upon epalrestat treatment bringing overall glycosylation toward the control fibroblasts’ glycosylation profile. Sorbitol levels were increased in the urine of 74% of patients with PMM2‐CDG and correlated with the presence of peripheral neuropathy, and CDG severity rating scale. In the child with PMM2‐CDG on epalrestat treatment, ataxia scores improved together with significant growth improvement. Urinary sorbitol levels nearly normalized in 3 months and blood transferrin glycosylation normalized in 6 months.InterpretationEpalrestat improved PMM enzyme activity, N‐glycosylation, and glycosylation biomarkers in vitro. Leveraging cellular glycoproteome assessment, we provided a systems‐level view of treatment efficacy and discovered potential novel biosignatures of therapy response. Epalrestat was well‐tolerated and led to significant clinical improvements in the first pediatric patient with PMM2‐CDG treated with epalrestat. We also propose urinary sorbitol as a novel biomarker for disease severity and treatment response in future clinical trials in PMM2‐CDG. ANN NEUROL 20219999:n/a–n/a

Abstract The selective estrogen receptor (ER) modulator, tamoxifen, is the only endocrine agent with approvals for both the prevention and treatment of premenopausal and postmenopausal estrogen-receptor positive breast cancer as well as for the treatment of male breast cancer. Endoxifen, a secondary metabolite resulting from CYP2D6-dependent biotransformation of the primary tamoxifen metabolite, N-desmethyltamoxifen (NDT), is a more potent antiestrogen than either NDT or the parent drug, tamoxifen. However, endoxifen’s antitumor effects may be related to additional molecular mechanisms of action, apart from its effects on ER. In phase 1/2 clinical studies, the efficacy of Z-endoxifen, the active isomer of endoxifen, was evaluated in patients with endocrine-refractory metastatic breast cancer as well as in patients with gynecologic, desmoid, and hormone-receptor positive solid tumors, and demonstrated substantial oral bioavailability and promising antitumor activity. Apart from its potent anticancer effects, Z-endoxifen appears to result in similar or even greater bone agonistic effects while resulting in little or no endometrial proliferative effects compared with tamoxifen. In this review, we summarize the preclinical and clinical studies evaluating endoxifen in the context of breast and other solid tumors, the potential benefits of endoxifen in bone, as well as its emerging role as an antimanic agent in bipolar disorder. In total, the summarized body of literature provides compelling arguments for the ongoing development of Z-endoxifen as a novel drug for multiple indications.

AbstractHigh‐dose methotrexate (HDMTX) pharmacokinetics (PKs), including the best estimated glomerular filtration rate (eGFR) equation that reflects methotrexate (MTX) clearance, requires investigation. This prospective, observational, single‐center study evaluated adult patients with lymphoma treated with HDMTX. Samples were collected at predefined time points up to 96 h postinfusion. MTX and 7‐hydroxy‐MTX PKs were estimated by standard noncompartmental analysis. Linear regression determined which serum creatinine‐ or cystatin C‐based eGFR equation best predicted MTX clearance. The 80 included patients had a median (interquartile range [IQR]) age of 68.6 years (IQR 59.2–75.6), 54 (67.5%) were men, and 74 (92.5%) were White. The median (IQR) dose of MTX was 7.6 (IQR 4.8–11.3) grams. Median clearance was similar across three dosing levels at 4.5–5.6 L/h and was consistent with linear PKs. Liver function, weight, age, sex, concomitant chemotherapy, and number of previous MTX doses did not impact clearance. MTX area under the curve (AUC) values varied over a fourfold range and appeared to increase in proportion to the dose. The eGFRcys (ml/min) equation most closely correlated with MTX clearance in both the entire cohort and after excluding outlier MTX clearance values (r = 0.31 and 0.51, respectively). HDMTX as a 4‐h infusion displays high interpatient pharmacokinetic variability. Population PK modeling to optimize MTX AUC attainment requires further evaluation. The cystatin C‐based eGFR equation most closely estimated MTX clearance and should be investigated for dosing and monitoring in adults requiring MTX as part of lymphoma management.

Single nucleotide variants in the open reading frames (ORFs) of pharmacogenes are important causes of interindividual variability in drug response. Because of the very large number of missense variants in ORFs, it is difficult to link the genotypes of these variants to their phenotypes using “one at a time” expression systems. Therefore, the functional characterization of variants of unknown significance in clinically important pharmacogenes remains a major challenge in pharmacogenomics. Deep mutational scanning (DMS) is a high‐throughput technique that make it possible to analyze hundreds of different missense variants in a parallel and scalable fashion. Engineered “landing pad” HEK 293T cells were used as a platform to integrate pooled variant libraries, resulting in one variant per cell for further assessment. We adapted this DMS system to analyze the function of missense variants in the ORFs of CYP2C9 and CYP2C19 . The ORFs of CYP2C9 and CYP2C19 were fused to green fluorescent protein, and individual variants with different fluorescence intensities were used to indicate different levels of protein expression. Pooled variant libraries were generated by nicking mutagenesis, and we then used recombinase to integrate the libraries into landing pad cells, one per cell. Multiplexed functional selection performed with Fluorescence Activated Cell Sorting separated cells into different bins by fluorescence readout at the single–cell level. Amplicon sequencing of DNA collected in each bin, followed by computational analysis of the frequency of variants appearing in each bin, was used to determine levels of protein expression. To identify potentially severely damaging variants for these two important pharmacogenes, we studied 243 missense variants in the CYP2C9 and CYP2C19 ORFs that had been identified by the Exome Aggregation Consortium Project and by the Mayo Clinic RIGHT 1K Study. We found that 13 of 115 CYP2C9 and 25 of 128 CYP2C19 missense variants displayed less than approximately 25% of the wildtype protein expression, a level that may have clinical relevance for drug metabolism. Variant calling by the DMS method for the severely damaging variants was compared with the results of individual variant assay by western blot and with the predictions of computational algorithms such as Polyphen and SIFT. Our results suggest that DMS is an efficient method for the high‐throughput identification of damaging ORF variants that might have potential clinical application in pharmacogenomics. Support or Funding Information Funded by NIH grant U19 GM61388 (The Pharmacogenomics Research Network), R01 GM28157, R01 GM125633, T32 GM08685 and by the Mayo Clinic Center for Individualized Medicine This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

10019 Background: Pevonedistat (PEV), a first in class inhibitor of NEDD8 activating enzyme (NAE), prevents the activation of Cullin-RING ligases (CRL) necessary for proteasome mediated degradation of key regulatory proteins important in cell survival. In adults with solid tumors, the maximum tolerated dose (MTD) in combination with chemotherapy is 20-25 mg/m2. Antitumor activity of PEV has been demonstrated in preclinical models of childhood cancer. In vivo additive activity has been demonstrated for PEV in combination with IRN and alkylating agents. The objectives of this study are to determine the MTD and recommended Phase 2 dose of PEV in combination with IRN and TMZ and describe the toxicities, pharmacokinetic (PK), and pharmacodynamics (PD) properties of this combination. Methods: We conducted a phase 1 trial of PEV in combination with IRN and TMZ in pediatric patients (pts) with recurrent or refractory solid tumors and brain tumors. During cycle 1, PEV was administered intravenously on days 1, 8, 10, and 12, with IRN (IV, 50mg/m2) and TMZ (orally, 100mg/m2), on days 8-12 of a 28 day cycle. In subsequent cycles, PEV was administered on days 1, 3, and 5, with IRN and TMZ on days 1-5 of a 21 day cycle. Dose escalation was determined using the Rolling 6 Design. Results: 30 pts enrolled. All pts were eligible and evaluable for cycle 1 dose limiting toxicity (DLT) assessment. Median (range) age was 13 (1-21) years; 19 (63%) were male. Eleven pts had brain tumors, and 19 pts had solid tumors. Six pts each enrolled on PEV dose levels (DL) 1 (15mg/m2), 2 (20mg/m2), 3 (25mg/m2) and 4 (35mg/m2) as well as an expanded PK cohort at DL4. Cycle 1 grade 3/4 toxicities include lymphopenia (n = 5), leukopenia (n = 4), neutropenia (n = 2), elevated ALT (n = 2), elevated AST (n = 1), diarrhea (n = 1), flu-like symptoms (n = 1). The most frequent non-dose limiting AEs in cycle 1 were anemia (87%), WBC decreased (77%), nausea (57%), diarrhea (53%), ALT increased (50%), AST increased (50%), and vomiting (50%). PK analyses showed the mean area under the curve at the 25 mg/m2 dose level on day 8 (in combination with irinotecan and temozolomide) was 1300 hr•ng/mL, half-life (T ½) was 5-6 hours, time to maximum concentration (Tmax) was 1 hour, and mean clearance was 20 L/hr/m2. There were 3 DLTs, 2 of which were related to protocol therapy (diarrhea and thrombocytopenia), among 12 patients on DL4. Thus the MTD was not exceeded at any dose level. PK at the 25 mg/m2 dose level are comparable to those in adult patients. PK from the 12 patients on DL4 (35mg/m2) as well as responses of all patients are pending. Conclusions: PEV in combination with IRN and TMZ is well tolerated in children with solid or brain tumors. PEV PK was not altered by the addition of irinotecan and temozolomide. Further PK and PD analyses are ongoing to establish the recommended phase 2 dose. Clinical trial information: NCT03323034.

10018 Background: Outcomes for children with relapsed/refractory (R/R) AML and MDS are poor and new therapies are needed. Pevonedistat is an inhibitor of the NEDD-8 activating enzyme, a key regulator of the ubiquitin proteasome system that is responsible for protein turnover, cell growth and survival. In preclinical models, pevonedistat was synergistic with cytarabine (AraC) and azacitidine (aza). The combination of pevonedistat + aza in adults with AML demonstrated improved responses compared to either single agent. We evaluated the feasibility, toxicity and pharmacokinetics (PK) of pevonedistat in combination with aza, fludarabine, AraC (Aza-FLA) in children with R/R AML and MDS. Methods: Pevonedistat 20 mg/m2, IV days 1, 3, 5, the recommended adult dose, was administered in combination with aza (75 mg/m2, days 1-5), fludarabine (30 mg/m2, days 6-10), and AraC (2000 mg/m2, days 6-10). Intrathecal AraC was administered at the start of therapy and additional doses given to patients with CNS leukemia. If < 33% of the initial 6 enrolled patients experienced dose limiting toxicity (DLT) during cycle 1 the regimen would be considered tolerable and 6 additional patients could enroll to further assess tolerability and PK. Pevonedistat PK was determined during cycle 1 following doses 1 and 5. Response was evaluated after cycle 1. Results: A total of 12 patients were enrolled, median age was 13 years (range 1-21). All patients received prior chemotherapy, median number of prior regimens was 2 (range 1-5) and 3 (25%) patients had prior hematopoietic stem cell transplant. Diagnoses were AML NOS (n = 10, 83%), acute monocytic leukemia (n = 1), and therapy related AML (n = 1). One of the initial 6 patients had DLTs (hypertension, GGT elevation, and proteinuria); pevonedistat 20 mg/m2 + Aza-FLA was considered tolerable. Six additional patients were enrolled, two had DLTs (weight loss, hypoxia). Overall, 3/12 (25%) of patients experienced DLTs. As expected, using the intensive Aza-FLA backbone, myelosuppression, electrolyte abnormalities, and hepatic transaminase elevation were common. Day 1 PK parameters (n = 12, mean±SD) were: Cmax= 223±91 ng/mL, AUC0-24h= 892±216 ng/hr/mL, T1/2=4.3±1.2 hours, CL = 23.2±6.9 L/hr/m2. PK parameters were similar following doses 1 and 5, for patients < 12 (n = 6) and ≥ 12 (n = 6) years, and to adult PK profiles. Ten patients were evaluable for response. The overall response rate was 30% (95% CI: 7,75) with 3 patients achieving a CR with incomplete hematologic recovery (CRi). Conclusions: Pevonedistat 20 mg/m2 combinedwith Aza-FLA was tolerable in children with R/R AML. The toxicity of the regimen was similar to other intensive AML regimens. PK parameters were similar among the two age groups and were comparable to adults. Within the confines of a phase I study, there was limited anti-leukemic activity of the combination of pevonedistat +Aza-FLA in R/R AML. Clinical trial information: NCT03813147.

10010 Background: Cabozantinib is an inhibitor of multiple receptor tyrosine kinases (RTKs) including MET, VEGFR2, RET, and AXL. Preclinical and clinical data support these RTKs as potential therapeutic targets; Safety, tolerability, and responses were demonstrated in a COG phase 1 trial. We conducted a multi-center open label phase 2 trial to determine the activity of cabozantinib in select pediatric solid tumors (NCT02867592). Methods: Patients age 2-30 years old with selected relapsed or refractory cancer that was measurable (RECISTv.1.1) were eligible. Using a Simon minimax design, patients were enrolled to six strata: Osteosarcoma (OS), Ewing sarcoma (EWS), rhabdomyosarcoma (RMS), non-rhabdomyosarcoma soft tissue sarcoma (NRSTS), Wilms tumor (WT), and rare tumor (a non-statistical stratum including tumors of specific histologies or molecular features). Cabozantinib (40 mg/m2/day) was administered on a continuous schedule (1 cycle = 28 days). For the OS stratum, activity was determined based on objective response rate (ORR, complete response (CR) + Partial response (PR)) or disease control success defined as at least stable disease (SD) for ≥ 4 months. For all other strata, the primary endpoint was ORR. Pharmacokinetics were performed in patients < 19 years. Results: Between May 2017- Oct 2020, 109 patients enrolled (105 eligible, 104 evaluable for response and toxicity). Median age was 15.8 (range 5.6-27.1) years; 55 were male. In the OS stratum, 10/29 (34%) patients had central review confirmed disease control ≥ 4 months (2 PR, 8 SD), exceeding the protocol-defined criteria for activity of cabozantinib in OS. Median duration of therapy was 3 cycles (range 1-28+). In EWS, RMS, NRSTS, and WT strata (n = 13 evaluable patients each) no PR or CR were observed. In the rare tumor stratum (n = 23), 1/4 patients with renal cell carcinoma, 1/1 patients with RET fusion positive papillary thyroid cancer had a PR, and 1 patient with medullary thyroid cancer had a delayed PR. SD ≥ 6 cycles was seen in patients with EWS (n = 2), NRSTS (n = 5), WT (n = 3), and hepatocellular carcinoma (n = 1). At data cutoff (12/31/2020), 430 treatment cycles were administered; two patients remain on therapy. Cycle 1 and later cycle dose limiting toxicities (DLT) were seen in 20 (19%) and 39 (38%) patients, respectively. Common DLT were elevated liver enzymes, bilirubin, and lipase, hyponatremia, weight loss, anorexia, nausea, vomiting, wound dehiscence, palmar-plantar erythrodysesthesia, and pneumothorax. Day 1 pharmacokinetics (mean ± SD, n = 16) demonstrated a maximum plasma concentration of 556 ± 376 ng/ml, half-life 106 ± 102 hours, and area under the curve (AUC0-24h) 8093 ± 4368 ng•h/mL. Conclusions: Cabozantinib is active in patients with relapsed refractory OS and deserves further study in this disease. PRs were also seen in select carcinomas. Activity is limited in other sarcomas and WT. Clinical trial information: NCT02867592.

10008 Background: The NCI-Children’s Oncology Group (COG) Pediatric Molecular Analysis for Therapy Choice (MATCH) trial assigns patients age 1 to 21 years with relapsed or refractory solid tumors, lymphomas, and histiocytic disorders to phase 2 treatment arms of molecularly-targeted therapies based on genetic alterations detected in their tumor. Arm E evaluated the MEK inhibitor selumetinib (ARRY-142886) in patients whose tumors harbored activating alterations in the MAPK pathway ( ARAF, BRAF, HRAS, KRAS, NRAS, MAP2K1, GNA11, GNAQ hotspot mutations; NF1 inactivating mutations; BRAF fusions). Methods: Patients received selumetinib 25 mg/m2/dose (max 75 mg/dose) PO BID for 28-day cycles until disease progression or intolerable toxicity with response assessments obtained every 2-3 cycles. The primary endpoint was objective response rate (ORR); secondary endpoints included progression-free survival (PFS). Patients with low grade glioma were excluded. Results: A total of 21 patients (median age 14 years; range 5-21) were enrolled between 10/2017 and 8/2019, with 20 patients evaluable for response. Diagnoses were high grade glioma (HGG; n = 8), rhabdomyosarcoma (n = 7), adenocarcinoma (n = 2), and one each of MPNST, endodermal sinus/yolk sac tumor, plexiform neurofibroma (PN), and neuroblastoma. MAPK pathway alterations detected consisted of inactivating NF1 mutations (n = 8), hotspot mutations in KRAS (n = 8), NRAS (n = 3), and HRAS (n = 1), and BRAF V600E (n = 2). No objective responses were observed. Three patients had a best response of stable disease (HGG with NF1 mutation, 6 cycles; HGG with KRAS mutation, 12 cycles; PN with NF1 mutation, 13 cycles prior to removal for dose-limiting toxicity). Six-month PFS was 15% (95% CI: 4%, 34%). Adverse events that were deemed possibly, probably, or definitely attributable to study drug included one case each of grade 3 uveitis, lymphopenia, and thromboembolic event; one grade 4 CPK elevation; and one grade 5 thromboembolic event. Conclusions: Selumetinib did not result in tumor regression in this cohort of children and young adults with treatment-refractory tumors with activating MAPK pathway alterations. Of note, two patients with HGG initially had stable disease, but ultimately progressed after 6 and 12 cycles, respectively. Selumetinib has previously demonstrated activity in low grade glioma and PN and is now FDA-approved for PN. The results of our study indicate that MAPK pathway mutation status alone is insufficient to predict response to selumetinib monotherapy. It is likely that selumetinib and other MEK inhibitors will require combination with targeted or cytotoxic agents for optimal efficacy in children with persistent or progressive cancers after front-line chemotherapy. Clinical trial information: NCT03213691. Clinical trial information: NCT03155620.