Glycemia and Gluconeogenesis With Metformin and Liraglutide: A Randomized Trial in Youth-onset Type 2 Diabetes

OBJECTIVE

Elevated rates of gluconeogenesis are an early pathogenic feature of youth-onset type 2 diabetes (Y-T2D), but targeted first-line therapies are suboptimal, especially in African American (AA) youth. We evaluated glucose-lowering mechanisms of metformin and liraglutide by measuring rates of gluconeogenesis and β-cell function after therapy in AA Y-T2D.

METHODS

In this parallel randomized clinical trial, 22 youth with Y-T2D-age 15.3 ± 2.1 years (mean ± SD), 68% female, body mass index (BMI) 40.1 ± 7.9 kg/m2, duration of diagnosis 1.8 ± 1.3 years-were randomized to metformin alone (Met) or metformin + liraglutide (Lira) (Met + Lira) and evaluated before and after 12 weeks. Stable isotope tracers were used to measure gluconeogenesis [2H2O] and glucose production [6,6-2H2]glucose after an overnight fast and during a continuous meal. β-cell function (sigma) and whole-body insulin sensitivity (mSI) were assessed during a frequently sampled 2-hour oral glucose tolerance test.

RESULTS

At baseline, gluconeogenesis, glucose production, and fasting and 2-hour glucose were comparable in both groups, though Met + Lira had higher hemoglobin A1C. Met + Lira had a greater decrease from baseline in fasting glucose (-2.0 ± 1.3 vs -0.6 ± 0.9 mmol/L, P = .008) and a greater increase in sigma (0.72 ± 0.68 vs -0.05 ± 0.71, P = .03). The change in fractional gluconeogenesis was similar between groups (Met + Lira: -0.36 ± 9.4 vs Met: 0.04 ± 12.3%, P = .9), and there were no changes in prandial gluconeogenesis or mSI. Increased glucose clearance in both groups was related to sigma (r = 0.63, P = .003) but not gluconeogenesis or mSI.

CONCLUSION

Among Y-T2D, metformin with or without liraglutide improved glycemia but did not suppress high rates of gluconeogenesis. Novel therapies that will enhance β-cell function and target the elevated rates of gluconeogenesis in Y-T2D are needed.

Targeting Replication Stress and Chemotherapy Resistance with a Combination of Sacituzumab Govitecan and Berzosertib: A Phase I Clinical Trial

PURPOSE

Despite promising preclinical studies, toxicities have precluded combinations of chemotherapy and DNA damage response (DDR) inhibitors. We hypothesized that tumor-targeted chemotherapy delivery might enable clinical translation of such combinations.

PATIENTS AND METHODS

In a phase I trial, we combined sacituzumab govitecan, antibody-drug conjugate (ADC) that delivers topoisomerase-1 inhibitor SN-38 to tumors expressing Trop-2, with ataxia telangiectasia and Rad3-related (ATR) inhibitor berzosertib. Twelve patients were enrolled across three dose levels.

RESULTS

Treatment was well tolerated, with improved safety over conventional chemotherapy-based combinations, allowing escalation to the highest dose. No dose-limiting toxicities or clinically relevant ≥grade 4 adverse events occurred. Tumor regressions were observed in 2 patients with neuroendocrine prostate cancer, and a patient with small cell lung cancer transformed from EGFR-mutant non-small cell lung cancer.

CONCLUSIONS

ADC-based delivery of cytotoxic payloads represents a new paradigm to increase efficacy of DDR inhibitors. See related commentary by Berg and Choudhury, p. 3557.

Clinical protocol: Feasibility of evaluating abemaciclib neuropharmacokinetics of diffuse midline glioma using intratumoral microdialysis

Diffuse midline gliomas (DMG) are the most aggressive brain tumors of childhood and young adults, with documented 2-year survival rates <10%. Treatment failure is due in part to the function of the BBB. Intratumoral microdialysis sampling is an effective tool to determine brain entry of varied agents and could help to provide a better understanding of the relationship of drug permeability to DMG treatment responsivity. This is a non-randomized, single-center, phase 1 clinical trial. Up to seven young adult (18-39 years) patients with recurrent high-grade or diffuse midline glioma will be enrolled with the goal of 5 patients completing the trial over an anticipated 24 months. All patients will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. Patients will undergo resection or biopsy, placement of a microdialysis catheter, and 48 hours of dialysate sampling coupled with timed plasma collections. If intratumoral tumor or brain dialysate sampling concentrations are >10nmol/L, or tumor tissue studies demonstrate CDK inhibition, then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy and discontinued with evidence of radiologic or clinical disease progression. The poor survival associated with diffuse midline gliomas underscore the need for improved means to evaluate efficacy of drug delivery to tumor and peritumoral tissue. The findings of this novel study, will provide real-time measurements of BBB function which have the potential to influence future prognostic and diagnostic decisions in such a lethal disease with limited treatment options. Trial registration: Clinicaltrials.gov, NCT05413304. Registered June 10, 2022, Abemaciclib Neuropharmacokinetics of Diffuse Midline Glioma Using Intratumoral Microdialysis.

First-in-human phase 1 clinical trial of anti-core 1 O-glycans targeting monoclonal antibody NEO-201 in treatment-refractory solid tumors

BACKGROUND

NEO201 is a humanized IgG1 monoclonal antibody (mAb) generated against tumor-associated antigens from patients with colorectal cancer. NEO-201 binds to core 1 or extended core 1 O-glycans expressed by its target cells. Here, we present outcomes from a phase I trial of NEO-201 in patients with advanced solid tumors that have not responded to standard treatments.

METHODS

This was a single site, open label 3 + 3 dose escalation clinical trial. NEO-201 was administered intravenously every two weeks in a 28-day cycle at dose level (DL) 1 (1 mg/kg), DL 1.5 (1.5 mg/kg) and DL 2 (2 mg/kg) until dose limiting toxicity (DLT), disease progression, or patient withdrawal. Disease evaluations were conducted after every 2 cycles. The primary objective was to assess the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of NEO-201. The secondary objective was to assess the antitumor activity by RECIST v1.1. The exploratory objectives assessed pharmacokinetics and the effect of NEO-201 administration on immunologic parameters and their impact on clinical response.

RESULTS

Seventeen patients (11 colorectal, 4 pancreatic and 2 breast cancers) were enrolled; 2 patients withdrew after the first dose and were not evaluable for DLT. Twelve of the 15 patients evaluable for safety discontinued due to disease progression and 3 patients discontinued due to DLT (grade 4 febrile neutropenia [1 patient] and prolonged neutropenia [1 patient] at DL 2, and grade 3 prolonged (> 72 h) febrile neutropenia [1 patient] at DL 1.5). A total of 69 doses of NEO-201 were administered (range 1-15, median 4). Common (> 10%) grade 3/4 toxicities occurred as follows: neutropenia (26/69 doses, 17/17 patients), white blood cell decrease (16/69 doses, 12/17 patients), lymphocyte decrease (8/69 doses, 6/17 patients). Thirteen patients were evaluable for disease response; the best response was stable disease (SD) in 4 patients with colorectal cancer. Analysis of soluble factors in serum revealed that a high level of soluble MICA at baseline was correlated with a downregulation of NK cell activation markers and progressive disease. Unexpectedly, flow cytometry showed that NEO-201 also binds to circulating regulatory T cells and reduction of the quantities of these cells was observed especially in patients with SD.

CONCLUSIONS

NEO-201 was safe and well tolerated at the MTD of 1.5 mg/kg, with neutropenia being the most common adverse event. Furthermore, a reduction in the percentage of regulatory T cells following NEO-201 treatment supports our ongoing phase II clinical trial evaluating the efficiency of the combination of NEO-201 with the immune checkpoint inhibitor pembrolizumab in adults with treatment-resistant solid tumors.

TRIAL REGISTRATION

NCT03476681 . Registered 03/26/2018.

EXTH-100. EVALUATION OF PANOBINOSTAT PLASMA AND CEREBROSPINAL FLUID (CSF) PHARMACOKINETIC PROFILE FOLLOWING ADMINISTRATION OF THE CAPSULE FORMULATION FARYDAK® IN A NON-HUMAN (NHP) PRIMATE PRECLINICAL MODEL

Panobinostat is an HDAC inhibitor with dose-dependent pre-clinical activity against pediatric glioma. Reported pharmacokinetic (PK) profiles of panobinostat, including CSF penetration, have varied. We hypothesized that this variability resulted from the utilization of differing panobinostat formulations. For comparison to the USP grade powdered formulation PK profile formerly reported (Rodgers, et al., Cancer Chemother Pharmacol. 2020 Apr;85(4):827-830) a plasma and CSF PK study was conducted with panobinostat administered as the capsule formulation, Farydak®, utilizing the same non-human primate (NHP) model, study design, analytical methods, and analysis.

METHODS

Three NHP previously developed for serial CSF access via a lateral ventricular CSF reservoir (n=2), or lumbar CSF port (n=1) received panobinostat orally (1.6 mg/kg, Human Dose Equivalent: 32 mg/m2) followed by serial paired plasma and CSF sample collections from 0-72 hours. Samples were quantified by LC-MS/MS. PK parameters were determined via noncompartmental analysis.

RESULTS

Mean plasma and CSF PK parameters Tmax (h), Cmax (nM), and AUCinf (h*nM/mg) are reported and compared to the corresponding PK parameters from the USP grade powdered formulation study formerly reported. Capsule Formulation: Plasma - Tmax: 5.3 □ 1.2, Cmax: 20 □ 1.9, AUClast: 14.5 □ 11.1, AUCinf: 15.2 □ 11.4 CSF - Tmax: 5.0 □ 3.6, Cmax: 1.7 □ 0.3, AUClast: 0.54 □ 0.47, AUCinf: unable to calculate Powdered Formulation – Mean PK of all dose levels formerly reported: Plasma -Tmax: 1.06 □ 0.13, Cmax: 1.27 □ 0.6, AUCinf: 7.7 □ 2.7 CSF - Cmax and Tmax: Unable to determine. Single quantifiable sample across all studies. AUCinf: unable to calculate.

CONCLUSION

The plasma and CSF Tmax, Cmax, the plasma AUCinf, and the CSF AUClast for panobinostat were increased following oral administration of the capsule formulation of panobinostat, Farydak®, compared to USP grade powder formulation of the drug.

EXTH-102. PLASMA AND CEREBROSPINAL FLUID (CSF) PHARMACOKINETICS (PK) OF MIRDAMETINIB IN A NON-HUMAN PRIMATE (NHP) MODEL

Mirdametinib is a MEK inhibitor with reported CSF penetration in pre-clinical models. Murine studies reported ERK phosphorylation inhibition in brain tissue at 1.15 nM (0.73 ng/mL) and tumor cell lines at 0.33–0.59 nM (0.16-0.28 ng/mL). A phase II clinical trial evaluating mirdametinib for neurofibromatosis type 1-related plexiform neurofibromas reported a 42% partial response rate and a mean plasma exposure (AUC0-12h) of 443 h*ng/mL. This study determined the plasma and CSF pharmacokinetic (PK) profile of mirdametinib in a non-human primate (NHP) model where CSF penetration serves as a proxy for CNS penetration.

METHODS

Four NHP received mirdametinib PO q.d, 0.50 mg/kg, in serial studies as a single dose (Single-Dose), three doses (Multiple-Dose), or IV, 0.20 mg/kg, followed by paired plasma and CSF sample collections through 96 hours. Mirdametinib was quantified by LC-MS/MS. PK parameters were calculated via noncompartmental methods. Plasma protein binding was determined by rapid equilibrium dialysis.

RESULTS

Mean □ standard deviation values reported. Three subjects were evaluable for both plasma (total and unbound) and CSF drug concentrations. Plasma – AUClast: Single-Dose 500.3 □ 253.4 and IV 552.3 □ 43 h*ng/mL; AUCtau: Multiple-Dose 456.3 □ 120.6 h*ng/mL. CSF Cmax (ng/mL): Single-Dose 0.43 □ 0.18, IV 2.0 □ 1.8, Multiple-Dose 0.56 □ 0.18. CSF Penetration (%): Single-Dose 1.3 □ 0.45, IV-1.6 □ 0.95 (AUCcsf-last:AUCplasma-last); Multiple-Dose 1.3 □ 0.56 (AUCcsf-tau:AUCplasma-tau). CSF/unbound plasma ratios ranged from 2.5-3.0 Plasma free fraction (%): 0.52 □ 0.1.

CONCLUSION

Notable mirdametinib CSF penetration was demonstrated in this NHP model. A higher CSF to unbound plasma ratio suggests that the efflux of mirdametinib from the CSF was delayed. The NHP CSF Cmax approached the ERK phosphorylation inhibition concentrations previously reported. The ability of this NHP model to predict human PK parameters was demonstrated via the comparable NHP to patient plasma exposure reported in the Phase II clinical trial.

Biological Effects of Modifications of the Englerin A Glycolate

Modifications at the glycolate moiety of englerin A were made to explore variations at the most sensitive site on the molecule for activity in the NCI 60 screen, wherein englerin A is highly potent and selective for renal cancer cells. Replacement of the glycolate by other functionalities as well as esterification of the glycolate hydroxyl yielded compounds which displayed excellent selectivity and potency compared with the natural product. TRPC4/5 ion channel experiments with five compounds showed delayed or reduced agonism with TRPC5, at much higher concentrations than englerin A. With TRPC4, these compounds all had no effect at 10 μM. The same compounds were not detectable in mouse serum after a single oral dose of 12.5 mg/kg. At 100 mg/kg p.o., no toxicity was observed, and blood levels were barely detectable. Intravenous administration led to toxicity but at substantially lower doses than for englerin A.

DDEL-04. Pharmacokinetic/Pharmacodynamic analysis of the DNA methyltransferase inhibitor 5-azacytidine shows adequate brain tissue penetration with intravenous administration in a DIPG mouse patient-derived xenograft model

One of the biggest obstacles in developing effective therapies for CNS tumors is drug delivery due to the enigmatic challenge of penetrating the blood-brain barrier. 5-azacytidine is a DNA methyltransferase inhibitor which was the first epigenetic targeting chemotherapeutic approved by the FDA. Altered DNA methylation is a hallmark of many cancers, including diffuse intrinsic pontine glioma (DIPG). 5-azacytidine has been shown to be active in DIPG cell lines, with only modest in-vivo activity. We have previously shown in a non-human primate model that intravenous (IV) administration of 5-azacitidine does not result in measurable CSF penetration, while intrathecal (IT) administration does and is well tolerated. To follow up these studies in a tumor-bearing mouse model (HSJD DIPG007), we performed pharmacokinetic (PK) and pharmacodynamic (PD) analysis following IV vs. IT administration. Forty mice were randomized to receive four weekly doses of IV 5-azacytidine (25 mg/kg), IT 5-azacytidine (40 μg), or corresponding vehicle controls. Four mice from each arm were sacrificed 30 minutes after the last dose and brain tissue was collected for PK/PD analysis. Drug concentration was quantified using ultra-high-performance liquid chromatography with tandem mass spectrometric detection, while pharmacodynamic methylation profiling was performed using the Infinium MethylationEPIC BeadChip (850K). Brain tissue concentrations were comparable between IV (7.6-58.0 pg/mg) and IT (6.9-63.9 pg/mg) dosing. Methylation profiling unexpectedly showed a significantly more pronounced pharmacodynamic effect with IV dosing vs. IT, with a mean decrease of 13.6% vs. 2.6% in global DNA methylation score (GDMS = percentage of highly methylated (beta ≥ 0.7) genomic loci) compared to vehicle controls. For the remaining mice, there was no significant difference in survival. Our results are encouraging that phenotypically relevant demethylating effects can be achieved in the CNS with IV 5-azacytidine administration; however, further research is needed to develop promising combination strategies in DIPG.

EXTH-64. COMPARISON OF PANOBINOSTAT CSF PENETRATION WITH CNS PENETRATION FOLLOWING SYSTEMIC ADMINISTRATION IN A PRE-CLINICAL NON-HUMAN PRIMATE MODEL

Targeted therapies developed for diffuse midline gliomas (DMG) expressing H3K27M have focused on histone deacetylase inhibitors (HDACi). High-throughput drug screening with patient derived DMG cell lines identified the HDACi panobinostat as a prominent clinical agent as well as pre-clinical studies with orthotopic mouse tumors models proving efficacious. Diametrically there is a pronounced lack of measurable panobinostat CSF concentrations in a non-human primate (NHP) non-tumor bearing pre-clinical model and in pediatric brain tumor patients. Notwithstanding, adult and pediatric glioma clinical trials and clinical observation with panobinostat alone or in combination have demonstrated minor responses. Pharmacokinetic models utilize the premise that CSF drug penetration is a surrogate of CNS drug penetration. However, the direct correlation between CSF and CNS drug levels is undefined especially in lieu of geographic CNS extracellular fluid drug variability previously demonstrated in the same NHP pre-clinical model. Utilizing the same NHP model, this study sought to compare panobinostat CSF penetration to CNS penetration via analysis of homogenized normal cerebrum, cerebellum, and brainstem tissue utilizing LC-MS/MS. METHODS: Panobinostat was administered orally as a single dose to three non-human primates. Pre panobinostat plasma and CSF were collected. Following panobinostat administration (1-hr Tmax) CSF, cerebrum, cerebellum, and brain stem tissue were collected as well as plasma to confirm the presence of panobinostat. Tissue slices were individually homogenized and panobinostat extracted via protein precipitation. Plasma, CSF, and tissue panobinostat concentrations were quantified using a LC-MS/MS assay. The lower limit of quantitation (LLOQ) for plasma-0.1 ng/ml, CSF-0.5 ng/ml, and tissue-10.0 pg/mg. RESULTS: Panobinostat was quantifiable in plasma (n=2) at the 1 hour (20.033 ng/mL and 0.153 ng/mL). CSF and CNS tissue samples were below the LLOQ for panobinostat in all samples. CONCLUSIONS: Panobinostat was not measurable from CSF and homogenized brain tissue in a non-tumor bearing NHP model at 1-hour post-administration using LC-MS/MS.

EPCT-16. LENALIDOMIDE ACTIVITY IN PILOCYTIC ASTROCYTOMA AND OPTIC PATHWAY GLIOMAS: REPORT ON CHILDREN’S ONCOLOGY GROUP ACNS1022

Children with low-grade glioma have excellent survival rates but often suffer from the morbidity of treatment, particularly from cytotoxic chemotherapies. Targeted agents appear to have some activity but the long-term effects of inhibiting normal developmental pathways are unknown. Lenalidomide is an oral immunomodulatory agent with additional properties including anti-angiogenesis. Phase I studies indicated greater tolerability of this agent compared to adults, and a potential dose-response effect. We performed a Phase 2 trial of lenalidomide in children with pilocytic astrocytoma and optic pathway gliomas who failed initial therapy. The primary objective was to determine the objective response rate of children randomized to Regimen A low-dose (20 mg/m² /dose) or Regimen B high-dose (115 mg/m² /dose) lenalidomide, each administering lenalidomide daily x 21 days of each 28-day course. Secondary objectives included estimation of event-free survival (EFS) in this population and correlation of plasma lenalidomide concentration with toxicity and outcome.

Results

74 eligible patients were enrolled (n=37 to each arm). The pre-defined activity level of interest was achieved for both arms. Objective responses were observed in both arms, with 4 partial responses in each. A total of n=18 patients completed 26 courses of therapy (Arm A, n=12, Arm B, n=6) The median number of courses on each arm was 14 (range 2–26) for Arm A and 11 for Arm B (range 1- 26). Of the 74 eligible patients who received study drug, 30 required a dose reduction for toxicity (Arm A, n=6, Arm B, n=24) and 16 discontinued treatment on protocol due to toxicity (Arm A, n=2, Arm B, n=14).

Conclusion

Lenalidomide demonstrates a sufficient level of activity in children with low-grade glioma to warrant further exploration in Phase 3 studies. Low-dose (20 mg/m²) lenalidomide appears to have better tolerability.

EPCT-09. CNS LEVELS OF PANOBINOSTAT IN A NON-HUMAN PRIMATE MODEL: COMPARISON OF BLOOD AND CEREBROSPINAL FLUID PHARMACOKINETIC METHODS AND MALDI MSI

Adequate exposure (effective concentration over time) of a therapeutic agent at its site of action is essential for antitumor efficacy. Given constraints of repeat tissue sampling, non-human primate models predictive of pharmacokinetics in pediatric patients have been utilized to assess central nervous system (CNS) exposure. Assessment of cerebrospinal fluid (CSF) drug levels have been used to extrapolate CNS penetration but the relationship of CSF drug levels with tissue distribution is unclear. Utilizing microdialysis, we previously demonstrated geographic variability of drug permeability across the blood:brain barrier (BBB), but this technique is complex and has a high standard deviation. We, therefore, explored a novel technique, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI), to compare plasma, CSF, and tissue drug levels in a terminal non-human primate model. Panobinostat, an HDAC inhibitor in clinical trials for DIPG/DMG, was selected for study as it has previously demonstrated poor CNS tissue penetration but suggested modest clinical activity.

Methods

Panobinostat (p.o., dose 1.6 mg/kg) was administered to non-tumor bearing primates (n=2). One hour following administration (Tmax), blood and CSF were collected, the animal euthanized, brain and spinal cord extracted, and immediately frozen at -80. Panobinostat distribution was mapped on ex vivo sagittal tissue sections using MALDI MSI. To provide specificity and degree of permeability, anatomical structures were segmented for analysis to determine drug concentrations. Blood, CSF and tissue levels of panobinostat were measured via LC-MS/MS.

Results

Segmentation analysis revealed quantifiable panobinostat, particularly in the lateral ventricles and choroid plexus, and also in the subventricular zone and brainstem, although the overall panobinostat concentration was below the limit of quantitation in these areas.

Conclusions

Although not reflected in CSF PK, panobinostat is widely distributed in brain tissue. MALDI MSI allows regional assessment of panobinostat penetration and complements CSF pharmacokinetics.

Abstract OT-26-03: Racial disparities in CYP3A variants in the metabolism of ribociclib in breast cancer patients

Background:Ribociclib is an inhibitor of the cyclin dependent kinases 4 and 6 (CDK 4/6) and is approved in combination with endocrine therapy for patients with advanced hormone receptor (HR) positive metastatic breast cancer (mBC). CYP3A inhibitors increase ribociclib area under the curve (AUC) by 3.2-fold; this is of clinical concern given possible associations between exposure and toxicity (e.g., QTc prolongation and neutropenia). Although there is an FDA recommendation to modify therapy for patients prescribed CYP3A inhibitors, it is unknown if modifications are needed in patients who intrinsically lack enzyme activity (e.g., genetic CYP3A5 poor metabolizers). CYP3A function is largely derived from CYP3A4 and CYP3A5 isozymes in adults. It is difficult to differentiate relative contributions of CYP3A4 and CYP3A5 on CYP3A function due to sequence homology (~ 84%) and overlapping substrate specificity. Genetic variations in CYP3A5 can translate into poor, intermediate, or normal CYP3A5 metabolism of different substrates and some pharmaceutics metabolized by CYP3A have dosing recommendations based on genotype. We hypothesize that patients harboring genetic variants causing CYP3A5 poor metabolism experience increased exposure to ribociclib and likely more toxicities. Race is likely to be significant factor when exploring ribociclib pharmacokinetics (PK) and the role of CYP3A. There are known race-based differences in CYP3A4 and CYP3A5, with alleles associated with CYP3A5 loss prevalent in European Americans (EA) and not in African Americans (AA). Ribociclib PK have not been adequately studied in AA with 3% of participants in the pivotal trials AA. We aim to determine the pharmacokinetic and pharmacogenomic association between ribociclib exposure and CYP3A variants in AA and EA patients. Our findings should allow clinicians to tailor treatments to maintain therapeutic doses while limiting toxicities. Methods:This prospective, multicenter, open-label pilot study will assess ribociclib (600 mg PO daily) PK and pharmacogenomics in female patients with HR+/HER2- mBC. This design will be two independent, race-based cohorts: 18 AA patients and 18 EA patients. Eligibility include: female, &gt;18, HR+/HER2- mBC and candidates for treatment with a CDK 4/6 inhibitor and endocrine therapy. Patients are ineligible if currently prescribed a medication that inhibits or induces the CYP3A isozymes, have baseline EKG abnormalities, or are otherwise considered to be ineligible for ribociclib. Participants will provide serial blood samples during the first cycle. Plasma samples will be analyzed via mass spectrometry to characterize the PK (e.g., AUC0-24, Cmax). Pharmacogenetic testing will be performed using the PharmacoScanTM microarray, which tests 4627 markers in 1191 genes, including 73 variants in CYP3A4 and CYP3A5. The primary endpoint will compare ribociclib AUC between CYP3A5 poor metabolizers vs. intermediate or normal CYP3A5 metabolizers within separate, race-based cohorts. Secondary endpoints include characterization of PK properties of ribociclib in the AA and EA populations. We also will seek to identify if CYP3A5, CYP3A4, or other variants are associated to different toxicity profiles. In addition, we will perform a hypothesis-generating PGx correlative analysis for potential biomarkers of ribociclib PK or toxicity. The primary outcome is powered to detect a minimum clinically meaningful change, a 2-fold change in AUC, which is less than the 3.2-fold change seen in the mentioned CYP3A drug interaction pharmacokinetic study. Based on CYP3A5 allelic frequencies, a sample size of 36 will provide 80% power to independently test the primary outcome in the two race-based cohorts.

Funding: Breast Cancer Research Foundation. Contact: Sandra Swain MD, sandra.swain@georgetown.edu

Citation Format: Ilana Schlam, D. Max Smith, Ian Chang, Asma Dilawari, Cody Peer, Tristan Sissung, Ming Tan, W. Douglas Figg, Sandra M. Swain. Racial disparities in CYP3A variants in the metabolism of ribociclib in breast cancer patients [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-26-03.

EXTH-25. THE CSF PENETRATION OF THE PROCASPASE-ACTIVATING COMPOUND (PAC-1) IN COMBINATION WITH TEMOZOLOMIDE (TMZ) IN A NONHUMAN PRIMATE CSF ACCESS MODEL

BACKGROUND

The synergistic activity of temozolomide (TMZ) administered in combination with procaspase-activating compound (PAC-1) has been reported in pre-clinical mouse models and canine patients, leading to clinical trials in adults with glioblastoma. To optimize pediatric clinical trial design, a translational pharmacokinetic CSF penetration study was conducted using a pre-clinical nonhuman primate non-tumor bearing CSF access model with TMZ and PAC-1 administered alone and in combination.

METHODS

Four male rhesus macaques with CSF lateral ventricular reservoirs received PAC-1, 15 mg/kg orally [Human Equivalent Dose (HED) 558 mg/m2/day] or TMZ, 1-hr IV infusion, 7.5 mg/kg (HED 150 mg/m2) as single and combination agent administration. Paired plasma and CSF samples were collected for 0–96 hours. PAC-1 and TMZ were quantified by LC-MS/MS. Pharmacokinetic parameters were calculated using noncompartmental methods. Statistics were determined via Mann-Whitney test.

RESULTS

(Mean ± Standard Deviation): For TMZ: Plasma AUC0-24 (hr*ng/ml) single agent (n=4): 28590 ± 4888 and in combination (n=4): 32736 ± 10147. CSF AUC0-24 (hr*ng/ml) single agent (n=4):14406 ± 1279 and in combination (n=4):15614 ± 1767. CSF penetration (% AUCCSF: AUCPLASMA) single agent: 50.9% ± 2.2 and in combination:49.6% ± 8.4. For PAC-1: Plasma PAC-1 AUC0-24 (hr*ng/ml) single agent (n=4): 2556 ± 2157 and in combination (n=4): 1947 ± 1311. CSF PAC-1 AUC0-24 (hr*ng/ml) single agent (n=2): 8.7 ± 1.1 and in combination (n=3):12.9 ± 10.2. CSF penetration single agent: 0.2% ± 0.03 and in combination: 0.4% ± 0.38. CSF PAC-1 tlag and Tmax pharmacokinetic parameters decreased with concurrent TMZ administration.

CONCLUSIONS

In this non-tumor bearing pre-clinical nonhuman primate model the CSF penetration of PAC-1 was low and not notably affected by the concurrent administration of TMZ. TMZ CSF penetration for single administration was within previously reported ranges and also appeared unaffected when administered in combination with PAC-1.

EXTH-65. PLASMA AND CEREBROSPINAL FLUID PHARMACOKINETICS COMPARISON OF BRAF AND MEK INHIBITORS FOLLOWING SINGLE AND EXTENDED ADMINISTRATION IN A PRE-CLINICAL NON-HUMAN PRIMATE MODEL

BACKGROUND

Aberrations in the MAPK signaling pathway are present in adult and pediatric CNS tumors. The BRAF and MEK inhibitors Dabrafenib, Vemurafenib, Selumetinib and Trametinib, alone or in combination, have demonstrated clinical efficacy. However, minimal CSF penetration has been demonstrated in pre-clinical models with single dose administration. CSF penetration of these agents was compared following single and extended oral administration in a nonhuman CSF Lateral Reservoir model to determine if CSF penetration increases at steady state.

METHODS

Agents were administered orally, to each subject (n=9), in single or multiple doses, as serial single agent studies, with washout periods between studies. The following dosages (Human equivalent dose HED) were utilized in the studies: Single Dosage-Selumetinib 2.5 mg/kg (50.0 mg/m2), Dabrafenib 8.0 mg/kg (160 mg/m2), Vemurafenib 26 mg/kg (520 mg/m2), Trametinib 0.06 and 0.12 mg/kg (1.2 and 2.4 mg/m2). Extended dosages-Selumetinib 2.5 mg/kg BID x 3 days (50.0 mg/m2), Dabrafenib 4.0 mg/kg BID x 2 days (160 mg/m2/day), Vemurafenib 26 mg/kg BID x 3 days (520 mg/m2), Trametinib 0.05 mg/kg x 10 days BID (1.0mg/m2). Paired serial plasma and CSF samples were collected. Agents were quantified by uHPLC-MS/MS. Pharmacokinetic parameters were calculated via noncompartmental methods. Plasma exposure reported as Area Under the Curve (AUC) and CSF penetration as ratio of CSF:plasma AUC. Statistical significance determined by t-test.

RESULTS

Single administration AUCinf/D (hr*ng/ml/mg) vs. extended administration AUCtau/D (hr*ng/ml/mg) for each agent: Vemurafenib-Plasma 30.9–351.4 vs.29.2–379.7, CSF-non-quantifiable; Dabrafenib-Plasma 29.3–102.6 vs.3.4–58.2, CSF-0.12–0.54 vs 0.04–0.19, % CSF:Plasma-0.3–0.84 vs.0.32–1.3; Trametinib-Plasma AUC indeterminable, CSF-non-quantifiable; Selumetinib-Plasma 69.8–133.0 vs.26.5–81.2; CSF-AUC indeterminable vs. 0.37–0.86, % CSF:Plasma-Indeterminable vs. 0.78–1.4. T-test: A downward trend in Dabrafenib and Selumetinib plasma AUC and a marked upward trend in Selumetinib CSF AUC.

CONCLUSIONS

With the exception of Selumetinib, the CSF exposure of BRAF and MEK inhibitors studied did not markedly increase following extended dosing.

A phase I study of the PD-L1 inhibitor, durvalumab, in combination with a PARP inhibitor, olaparib, and a VEGFR1-3 inhibitor, cediranib, in recurrent women's cancers with biomarker analyses

BACKGROUND

Strategies to improve activity of immune checkpoint inhibitors are needed. We hypothesized enhanced DNA damage by olaparib, a PARP inhibitor, and reduced VEGF signaling by cediranib, a VEGFR1-3 inhibitor, would complement anti-tumor activity of durvalumab, a PD-L1 inhibitor, and the 3-drug combination would be tolerable.

METHODS

This phase 1 study tested the 3-drug combination in a 3 + 3 dose escalation. Cediranib was taken intermittently (5 days on/2 days off) at 15 or 20 mg (dose levels 1 and 2, respectively) with durvalumab 1500 mg IV every 4 weeks, and olaparib tablets 300 mg twice daily. The primary end point was the recommended phase 2 dose (RP2D). Response rate, pharmacokinetic (PK), and correlative analyses were secondary endpoints.

RESULTS

Nine patients (7 ovarian/1 endometrial/1 triple negative breast cancers, median 3 prior therapies [2-6]) were treated. Grade 3/4 adverse events include hypertension (1/9), anemia (1/9) and lymphopenia (3/9). No patients experienced dose limiting toxicities. The RP2D is cediranib, 20 mg (5 days on/2 days off) with full doses of durvalumab and olaparib. Four patients had partial responses (44%) and 3 had stable disease lasting ≥6 months, yielding a 67% clinical benefit rate. No significant effects on olaparib or cediranib PK parameters from the presence of durvalumab, or the co-administration of cediranib or olaparib were identified. Tumoral PD-L1 expression correlated with clinical benefit but cytokines and peripheral immune subsets did not.

CONCLUSIONS

The RP2D is tolerable and has preliminary activity in recurrent women's cancers. A phase 2 expansion study is now enrolling for recurrent ovarian cancer patients.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02484404. Registered June 29, 2015.

A phase I study of mesothelin-targeted immunotoxin LMB-100 in combination with nab-paclitaxel for patients with previously treated advanced pancreatic cancer

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Background: LMB-100 is a Pseudomonas exotoxin A-based immunotoxin that targets mesothelin (MSLN). MSLN is expressed by >75% of pancreatic adenocarcinomas (PDAC). LMB-100 kills MSLN-expressing cells by irreversibly modifying elongation factor-2 to halt protein synthesis. Phase I studies of LMB-100 defined the maximum tolerated dose (MTD) of 140 mcg/kg IV given on D1, 3 and 5 of a 21-day cycle. Development of anti-drug antibodies (ADAs) limited patient drug exposure beyond cycle 2. Our pre-clinical data showed that combination of LMB-100 with a taxane resulted in synergistic anti-tumor activity. Methods: We conducted a phase I single center study (standard 3+3 design) to determine the MTD of LMB-100 given with nab-paclitaxel in patients with previously treated advanced PDAC. LMB-100 was given on D1, 3 and 5 of a 21-day cycle, and nab-paclitaxel (125 mg/m2) on D1 and D8. Initial patients could receive a maximum of 4 cycles, but subsequently a 2-cycle maximum was employed. Results: Fourteen patients (median age 58) were enrolled. Two of 6 patients experienced DLTs at the 100 mcg/kg dose of LMB-100 (myalgia- 2 pts, fatigue- 1 pt, hypotension- 1 pt; all grade 3). One of 8 patients had DLT at the 65 mcg/kg dose (edema, urine output decrease- both grade 3). Other toxicities related to LMB-100 included hypoalbuminemia, edema-associated weight gain, hyponatremia, fatigue, drug fever, infusion-related reaction, hypophosphatemia, nausea and anorexia. One patient died on treatment from complications of bowel perforation attributed to cancer. All patients achieved detectable serum levels of LMB-100 during the first cycle, even those with pre-existing ADAs, and 5 of 8 did so during cycle 2. One patient receiving the 65 mcg/kg dose had a confirmed partial response, and CA 19-9 dropped by > 50% in 5 of 8 evaluable patients. Conclusions: MTD of LMB-100 is 65 mcg/kg given with nab-paclitaxel on this schedule. Anti-tumor activity was observed. A phase II cohort is currently being accrued. Clinical trial information: NCT02810418.

Pilot Study Comparing Systemic and Tissue Pharmacokinetics of Irinotecan and Metabolites after Hepatic Drug-Eluting Chemoembolization

Differences in drug metabolism associated with UGT1A1 polymorphism could result in individualized local response to hepatic chemoembolization with irinotecan-eluting beads (DEBIRI) or predictable toxicities. Five patients with inoperable hepatic metastases from colorectal or anal malignancies treated with DEBIRI were assessed for UGT1A1 mutations. No difference in area under the curve (AUC) for SN38 in normal liver and tumor tissue samples was noted with variant or wild-type UBT1A1 (P = .16 and P = .05, respectively). Plasma SN-38 AUC was significantly lower in wild-type compared to variant patients (P < .0001). UGT1A1 genotype may not be predictive of hematologic toxicity after DEBIRI.

Abstract P1-01-01: The blood-Tumor barrier as a therapeutic target to improve therapy of brain metastases of breast cancer

Objectives: Brain metastases of breast cancer demonstrate low and heterogeneous levels of permeability to drugs in mouse models and human craniotomies. The Blood-Brain Barrier (BBB), the protective lining of CNS blood vessels, impedes drug entry into the normal brain. When a metastasis forms, the BBB is locally altered to a poorly characterized Blood-Tumor Barrier (BTB). Quantitative experimental models indicate that most brain metastases have increased permeability over the normal BBB, but BTB permeability is both heterogeneous and ˜2 logs less than that of systemic metastases. We have interrogated three hematogenous models of brain metastasis of breast cancer to ask (1) whether the BTB is an ordered structure or a random breakdown of the BBB; (2) among brain metastases, whether consistent differences underlie the BTBs of lesions with low- and high permeabilities to fluorescent markers and drugs; (3) if alterations in BTB composition can functionally change its permeability. Our long term goal is to enhance uptake of drugs into brain metastases to effective levels.

Results: When uninvolved brain was compared with any brain metastasis, alterations in endothelial, pericytic, astrocytic, and microglial components of the BBB were observed. Both the pericyte and astrocyte components of the BTB were consistently altered with increased permeability: When metastases with relatively low and high permeability were compared, increased expression of a desmin+ subpopulation of pericytes was associated with higher permeability (231-BR6 P=0.0002; JIMT-1-BR3 P = 0.004; SUM190-BR3 P=0.008). A trend toward reduced CD13+ pericytes was observed in highly permeable metastases (231-BR6 P =0.014; JIMT-1-BR3 P =0.002, SUM190-BR3, NS). For GFAP+ astrocytes in the neuroinflammatory response surrounding metastases, no overall difference in cell number was observed between low and high permeability lesions. However, gene expression profiling of laser capture microdissected low and high permeabililty lesions demonstrated overexpression of the sphingosine-1 phosphate receptor 3 (S1P3) in the astrocytes of highly permeable lesions, which was confirmed at the protein expression level in all three models (231-BR6 P=0.034; JIMT-1-BR3 P = 0.01; SUM190-BR3 P=0.016). Inhibition of S1P3 via S1PR3 shRNA or a selective antagonist (TY-52156) functionally tightened the BTB in an in vitro model. Administration of TY-52156 to mice harboring 231-BR6 brain metastases had no effect on metastasis number, but decreased uptake of Texas Red Dextran dye into metastases (P=0.016). S1P3 mediated its effects on BTB permeability through astrocytic secretion of IL-6 and CCL2, which altered endothelial expression and localization of adhesive proteins, a potentially translatable pathway. Both desmin+ pericytes and S1P3+ astrocytes are present in human craniotomy specimens.

Conclusions: These experiments demonstrate that the BTB is a structure with consistent properties, and that further consistent changes underlie the transition from a low to high permeability BTB. While proof of principle, S1P3 inhibition studies indicate that the BTB permeability can be functionally modulated in vivo.

Citation Format: Steeg PS, Lyle TR, Paranjapee A, Lockman PR, Duchnowska R, Brastianos PK, Peer C, Figg WD, Pauly GT, Schneider JP, Smith QR, Gril B. The blood-Tumor barrier as a therapeutic target to improve therapy of brain metastases of breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-01.

The effect of an adenosine A2A agonist on intra-tumoral concentrations of temozolomide in patients with recurrent glioblastoma

Background

The blood–brain barrier (BBB) severely limits the entry of systemically administered drugs including chemotherapy to the brain. In rodents, regadenoson activation of adenosine A_2A receptors causes transient BBB disruption and increased drug concentrations in normal brain. This study was conducted to evaluate if activation of A_2A receptors would increase intra-tumoral temozolomide concentrations in patients with glioblastoma.

Methods

Patients scheduled for a clinically indicated surgery for recurrent glioblastoma were eligible. Microdialysis catheters (MDC) were placed intraoperatively, and the positions were documented radiographically. On post-operative day #1, patients received oral temozolomide (150 mg/m²). On day #2, 60 min after oral temozolomide, patients received one intravenous dose of regadenoson (0.4 mg). Blood and MDC samples were collected to determine temozolomide concentrations.

Results

Six patients were enrolled. Five patients had no complications from the MDC placement or regadenoson and had successful collection of blood and dialysate samples. The mean plasma AUC was 16.4 ± 1.4 h µg/ml for temozolomide alone and 16.6 ± 2.87 h µg/ml with addition of regadenoson. The mean dialysate AUC was 2.9 ± 1.2 h µg/ml with temozolomide alone and 3.0 ± 1.7 h µg/ml with regadenoson. The mean brain:plasma AUC ratio was 18.0 ± 7.8 and 19.1 ± 10.7% for temozolomide alone and with regadenoson respectively. Peak concentration and T_max in brain were not significantly different.

Conclusions

Although previously shown to be efficacious in rodents to increase varied size agents to cross the BBB, our data suggest that regadenoson does not increase temozolomide concentrations in brain. Further studies exploring alternative doses and schedules are needed; as transiently disrupting the BBB to facilitate drug entry is of critical importance in neuro-oncology.

Electronic supplementary material

The online version of this article (10.1186/s12987-017-0088-8) contains supplementary material, which is available to authorized users.

Abstract 4330: Astrocytic S1P3 regulates blood-brain/tumor barrier permeability

Introduction: Incidence of breast cancer brain metastasis is increasing owing to prolonged life-span and better detection techniques. Prognosis of patients with brain metastases is extremely poor with median survival time of one year. One of the major impediments in treating brain metastases is presence of blood-brain/tumor barrier that limits the permeability of chemotherapeutic drugs into the brain parenchyma. Understanding the mechanisms that regulate blood-brain/tumor barrier permeability in context of brain metastases is imperative to developing successful therapy.

Methods: Mouse models with brain-tropic sublines of MDA-MB-231 (231), JIMT-1, and SUM190 were used to generate breast cancer brain metastases. Using laser capture microscopy, the permeable and non-permeable lesions from mouse brains were isolated and profiled for gene expression using microarray. Immortalized human brain endothelial cells, astrocytes, and pericytes were used for developing in vitro blood-brain/tumor barrier model along with spheres generated with 231-BR6 or JIMT-1-BR3 cells. Secreted cytokines were evaluated using human cytokine profiler. Transendothelial electrical resistance (TEER) was measured using EVOM2 volt/ohm meter.

Results: Gene expression profiling and immunostaining of mouse brains, harboring breast cancer metastases showed that astrocytes at permeable regions express elevated S1P3. Pharmacological inhibition of S1P3 using antagonist TY-52156 (10mg/kg) in mice bearing 231-BR6 brain metastases showed reduction in 3KDa Texas red dextran (TRD) uptake. To investigate the role of S1P3 in regulating barrier permeability, we established in vitro blood-brain/tumor barrier models. Treatment of astrocytes with TY-52156 (2μM) significantly increased mean TEER values (33.9 to 55.8 Ω.cm2; p&lt;0.001, after 24 hrs), while there was a decrease in permeability for TRD (1.9 fold; p&lt;0.0001) and doxorubicin (1.3 folds; p&lt;0.05). Immunostaining on endothelial monolayer showed increased membranous ZO-1 and VE-cadherin expression. The dynamics of increase in TEER was faster when 231-BR6 spheres were included. We observed similar results when S1P3 was knocked down using shRNA. Astrocytes with down-modulated S1P3 showed decreased secretion of various cytokines including IL-6, IL-8, CCL2, CXCL1, and GM-CSF. Inhibition of these cytokines individually using neutralizing antibodies recapitulated the effects of S1P3 inhibition, while treatment of endothelial monolayer with activated cytokines increased the permeability. This study provides a proof of concept for role of S1P3 and downstream cytokine signaling in regulating blood-brain/tumor barrier permeability in breast cancer brain metastases.

Conclusion: Our study shows that astrocytic S1P3 regulates blood-brain/tumor barrier permeability in breast cancer brain metastases by modulating cytokine secretion. This observation might lead to discovery of novel strategies for augmenting drug efficacy.

Citation Format: Anurag N. Paranjape, Brunilde Gril, Stephan Woditschka, Emily Hua, Jeffrey C. Hanson, Xiaolin Wu, Renata Duchnowska, Priscilla K. Brastianos, David L. Liewehr, Seth M. Steinberg, Cody Peer, William D. Figg, Gary T. Pauly, Christina Robinson, Joel P. Schneider, Patricia S. Steeg. Astrocytic S1P3 regulates blood-brain/tumor barrier permeability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4330. doi:10.1158/1538-7445.AM2017-4330

Treatment With Carfilzomib-Lenalidomide-Dexamethasone With Lenalidomide Extension in Patients With Smoldering or Newly Diagnosed Multiple Myeloma

IMPORTANCE

Carfilzomib-lenalidomide-dexamethasone therapy yields deep responses in patients with newly diagnosed multiple myeloma (NDMM). It is important to gain an understanding of this combination's tolerability and impact on minimal residual disease (MRD) negativity because this end point has been associated with improved survival.

OBJECTIVE

To assess the safety and efficacy of carfilzomib-lenalidomide-dexamethasone therapy in NDMM and high-risk smoldering multiple myeloma (SMM).

DESIGN, SETTING, AND PARTICIPANTS

Clinical and correlative pilot study at the National Institutes of Health Clinical Center. Patients with NDMM or high-risk SMM were enrolled between July 11, 2011, and October 9, 2013. Median follow-up was 17.3 (NDMM) and 15.9 months (SMM).

INTERVENTIONS

Eight 28-day cycles were composed of carfilzomib 20/36 mg/m2 on days 1, 2, 8, 9, 15, and 16; lenalidomide 25 mg on days 1 through 21; and dexamethasone 20/10 mg (cycles 1-4/5-8) on days 1, 2, 8, 9, 15, 16, 22, and 23. Patients who achieved at least stable disease subsequently received 24 cycles of lenalidomide extended dosing.

MAIN OUTCOMES AND MEASURES

Primary end points were neuropathy of grade 3 or greater (NDMM) and at least very good partial response rates (SMM). Minimal residual disease was also assessed.

RESULTS

Of 45 patients with NDMM, none had neuropathy of grade 3 or greater. Of 12 patients with high-risk SMM, the most common of any-grade adverse events were lymphopenia (12 [100%]) and gastrointestinal disorders (11 [92%]). All patients with SMM achieved at least a very good partial response during the study period. Among the 28 patients with NDMM and the 12 with SMM achieving at least a near-complete response, MRD negativity was found in 28 of 28 (100% [95% CI, 88%-100%]), 11 of 12 (92% [95% CI, 62%-100%]) (multiparametric flow cytometry), 14 of 21 (67% [95% CI, 43%-85%]), and 9 of 12 (75% [95% CI, 43%-94%]) (next-generation sequencing), respectively. In patients with NDMM, 12-month progression-free survival for MRD-negative vs MRD-positive status by flow cytometry and next-generation sequencing was 100% vs 79% (95% CI, 47%-94%; P < .001) and 100% vs 95% (95% CI, 75%-99%; P = .02), respectively.

CONCLUSIONS AND RELEVANCE

Carfilzomib-lenalidomide-dexamethasone therapy is tolerable and demonstrates high rates of MRD negativity in NDMM, translating into longer progression-free survival in patients achieving MRD negativity. Carfilzomib-lenalidomide-dexamethasone therapy also demonstrates efficacy in high-risk SMM.

Abstract B43: ANG1005, a novel brain-penetrant drug conjugate, in CNS metastases from breast cancer: FLT-PET imaging as a predictor of response

Background:

The novel drug conjugate ANG1005 consists of 3 molecules of paclitaxel covalently linked to Angiopep-2. After binding to the low-density lipoprotein receptor-related protein, ANG1005 crosses the blood brain barrier (BBB) by endocytosis. A multi-center Phase II study, with the primary endpoint of intracranial response in patients with breast cancer brain metastases is in progress. At the NCI, a biomarker substudy is evaluating 18F-FLT (3'-Fluoro-3' deoxythymidine)-PET for response assessment.

Methods:

Patients with measurable brain metastases from breast cancer received ANG1005 at a dose of 550mg/m2 IV once every 21 days. Before and after cycle 1, all patients on study underwent imaging with 18F-FLT, a thymidine analog and novel imaging agent; retention of 18F-FLT correlating with DNA synthesis. In order to detect brain metastases and assess response to treatment, we compared FLT PET images with MRI-gadolinium contrast scans, obtaining both dynamic and static images. We determined the percentage (%) change after treatment with ANG1005; a decrease in ≥20% was considered significant.

Results:

Ten patients were enrolled on study. A total of 32 target and 20 non target CNS lesions in 10 patients were imaged and analyzed by MRI and FLT-PET.

At 30 minutes, SUVmax ranged from 0.8 to 6.3 at baseline (mean 2.64), and the SUV80%, (mean of top 20% SUV units) ranged from 0.7 to 5.12. The median% change from baseline to post one cycle of ANG1005 was -19.9% for SUVmax (range +85.4 to -67.7, and was median -20.2% for SUV80% (range 95.7 to -69%). Two patients had confirmed partial responses lasting 6 and 18 cycles, respectively. Six patients had stable disease and received a median of 6 cycles. Tumor reductions, as determined by MRI per CNS RECIST version 1.1 ranged from -5% to -60% in lesion size, compared to baseline. Both FLT-PET parameters correlated with the% change in MRI measurements in the target lesions (R2 = 0.64, P = 0.0002).

Conclusion:

The development of CNS-directed therapies designed to cross the BBB, such as the paclitaxel conjugate ANG1005, is a research priority. As contrast-enhanced MRI detection of brain metastases is representative of gadolinium leakage through the BBB, as opposed to actual tumor volume, better approaches are needed to evaluate drug efficacy. Pilot evaluations of FLT-PET imaging in this setting suggest that it is a promising tool that may serve as a complementary assessment method for breast cancer brain metastases going forward.

Citation Format: Ciara C. O'Sullivan, Maria Lindenberg, Christine Bryla, Nicole Davarpanah, Cody Peer, Nicholas Patronas, Laleh Amiri-Kordestani, Sanjeeve Balasubramaniam, Tito Fojo, William D. Figg, Peter Choyke. ANG1005, a novel brain-penetrant drug conjugate, in CNS metastases from breast cancer: FLT-PET imaging as a predictor of response. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B43.

A phase I study of TRC105 anti-endoglin (CD105) antibody in metastatic castration-resistant prostate cancer

OBJECTIVE

TRC105 is a chimeric immunoglobulin G1 monoclonal antibody that binds endoglin (CD105). This phase I open-label study evaluated the safety, pharmacokinetics and pharmacodynamics of TRC105 in patients with metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Patients with mCRPC received escalating doses of i.v. TRC105 until unacceptable toxicity or disease progression, up to a predetermined dose level, using a standard 3 + 3 phase I design.

RESULTS

A total of 20 patients were treated. The top dose level studied, 20 mg/kg every 2 weeks, was the maximum tolerated dose. Common adverse effects included infusion-related reaction (90%), low grade headache (67%), anaemia (48%), epistaxis (43%) and fever (43%). Ten patients had stable disease on study and eight patients had declines in prostate specific antigen (PSA). Significant plasma CD105 reduction was observed at the higher dose levels. In an exploratory analysis, vascular endothelial growth factor (VEGF) was increased after treatment with TRC105 and VEGF levels were associated with CD105 reduction.

CONCLUSION

TRC105 was tolerated at 20 mg/kg every other week with a safety profile distinct from that of VEGF inhibitors. A significant induction of plasma VEGF was associated with CD105 reduction, suggesting anti-angiogenic activity of TRC105. An exploratory analysis showed a tentative correlation between the reduction of CD105 and a decrease in PSA velocity, suggestive of potential activity of TRC105 in the patients with mCRPC. The data from this exploratory analysis suggest that rising VEGF level is a possible compensatory mechanism for TRC105-induced anti-angiogenic activity.

Abstract 2575: Results from the first-in-human phase I trials of recombinant human Interleukin 15 (rhIL-15) administered as a daily 30 minute intravenous infusion (IVB) for 12 consecutive days or as continuous intravenous infusion (CIV) for 240 hours in patients with refractory metastatic cancers

Preclinical laboratory experiments with Interleukin 15 (IL-15) have demonstrated significant immunotherapeutic potential for recombinant human IL-15 (rhIL-15) in cancer patients. We have completed a first-in-human (FIH), phase I dose escalation trial of E. coli produced rhIL-15 administered as a 30 minute intravenous bolus (IVB) infusion given daily for 12 consecutive days to patients with metastatic melanoma (MM) or renal cell carcinoma (mRCC). rhIL-15 treatment produced up to an 8-fold expansion of circulating NK cells, approximately 2 fold expansion of CD8+ CD45RO+ memory T-cells and up to 50 fold increases in serum level for multiple cytokines. Characteristic toxicities associated with cytokine treatment such as fever, rigors or chills, capillary leak, myalgias and blood pressure changes occurred at frequency and severity proportional to the dose of rhIL-15. Laboratory results showed early course transient leukopenia, lymphopenia, modest neutropenia, occasional thrombocytopenia and significant elevations of alanine and asparagine transaminase (ALT, AST) in a number of patients. Antibodies to rhIL-15 antibodies were not detected in any patient. The maximum tolerated dose for this schedule was 0.3 μg/kg/day with dose-limiting toxicities (DLTs) of grade 3 hypotension, thrombocytopenia, grade 3 or 4 ALT and AST elevation. There were no documented objective responses by RECIST criteria, but decreases in the sum of diameters for the marker lesions between 10 and 30% and improvement or clearance of parenchymal lung metastases were observed in several patients suggesting some antitumor activity.

A phase I dose escalation trial evaluating a 10 day (240 hour) continuous intravenous infusion (CIV) of rhIL-15 which is expected to produce greater expansion of CD8 effector cells and immune activation has been initiated. Patients treated at the first two dose levels have demonstrated improved clinical tolerability, immune activation; fewer laboratory abnormalities and no DLTs. Patient accrual and dose escalation to the third dose level are ongoing.

Citation Format: Kevin C. Conlon, Enrico Lugli, Steven A. Rosenberg, John C. Morris, Thomas Fleisher, Hugh Welles, Sigrid Dubois, Liyanage Perera, Carolyn Goldman, Bonita Bryant, Jean Decker, Joanna Shih, Tat'Yana Worthy, William Figg, Cody Peer, Michael Sneller, H. Clifford Lane, Jason Yovandich, Stephen Creekmore, Mario Roederer, Thomas A. Waldmann. Results from the first-in-human phase I trials of recombinant human Interleukin 15 (rhIL-15) administered as a daily 30 minute intravenous infusion (IVB) for 12 consecutive days or as continuous intravenous infusion (CIV) for 240 hours in patients with refractory metastatic cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2575. doi:10.1158/1538-7445.AM2014-2575

Phase I and pharmacokinetic study of sorafenib in Kaposi sarcoma

10588

Background: Kaposi sarcoma (KS) is a multifocal angioproliferative disorder. VEGFR2-3, PDGFR and c-kit are implicated in KS pathogenesis and inhibited by sorafenib (So). KS is commonly HIV-associated. The antiretroviral drug ritonavir (R) inhibits CYP3A4, and may affect So metabolism and tolerability. Methods: We performed a phase I study of So in KS. HIV+ patients (pts) were eligible if on combination antiretroviral therapy (cART) for >3 months with progressive KS or >4 months with no KS regression. Dose level 1 for pts on R-containing cART (R1) was So 200 mg daily, for pts not receiving R (NR1) So 200 mg every 12 hours. Treatment cycles were 21 days. So pharmacokinetic assessment performed cycle 1 day 8. Adverse event (AE) grade (Gr) by CTCAE v3.0 (2006-10) and v4.0 (2011-12). KS response graded by modified ACTG criteria. Results: 10 pts, R1 (8), NR1 (2). Baseline characteristics: median (med) (range) age 49 (35-72), CD4 in HIV+ 500 cells/uL (35, 747), time on cART 9 months (3.5, 27), previous KS therapies 2 (0-5). 9 HIV-infected, 8/9 HIV viral load <50 copies/mL. 6 had KS-associated edema. Med number cycles 4 (1, 13). Common AE at least possibly attributable to So: anemia, AST/ALT elevation, lipase elevation, hypertension, proteinuria, fatigue, infection, voice alteration. Dose-limiting toxicities (DLT): R1- Gr3 asymptomatic elevated lipase (1), Gr4 thrombocytopenia (1, likely due to multicentric Castleman disease); NR1- Gr3 hand-foot syndrome not resolved by week 6 (1). Other Gr 3-4 AE: R1- hand-foot syndrome (1), Gr3 thrombocytopenia (1), Gr3 transient cerebral ischemia (1), Gr3 hypertension (1); NR1- Gr3 hypertension (2). Best response: partial response (PR) (2), stable disease (SD)(5), progressive disease (1), not evaluable (2). Med duration SD 12 weeks (5, 33). 5/6 with KS-associated edema had objective decrease in edema. R was not associated with clear difference in So CMax or AUC at steady state. Conclusions: Preliminary estimate of PR or better is 20%. Even in some cases where KS did not respond, KS-associated edema improved. However, So was relatively poorly tolerated, with DLT observed at R1 and NR1, and these doses did not yield better responses than established therapies. Additional studies evaluating R’s effect on So metabolites are warranted. Clinical trial information: NCT00287495.

Phase I trial of belinostat in combination with cisplatin (Cis) and etoposide (Etop)

2527

Background: Histone deacetylase inhibitors (HDIs) are epigenetic therapies in development. To exploit the unique activity in impairing DNA repair, HDIs have been combined with chemotherapy. Belinostat is a potent HDI combined with Cis and Etop based on enhanced DNA damage and apoptosis in small cell lung cancer (SCLC) cells. Methods: Patients with relapsed/refractory cancer or previously untreated advanced stage SCLC were eligible. Belinostat was administered by continuous infusion (CIV) over 48h, from 400 mg/m2/24h, in cohorts of 3. Cis was administered on day 1 and Etop daily X3. Belinostat pharmacokinetics (PK) and several pharmacodynamic (PD) measures were assessed, including lysine acetylation in peripheral blood mononuclear cells (PBMCs) and γH2Ax staining in PBMCs and in hair follicles. Results: Five dose levels were explored in 20 patients with solid tumors, including 5 patients with SCLC, two who had no prior therapy. At the first dose level, dose-limiting toxicities (DLT) of gr 4 ANC in 1, and gr 3 HTN in 1 were observed. Cis and Etop were reduced to 60 mg/m2 and 80 mg/m2, respectively, and the dose level repeated without DLT. At the next dose level, 800 mg/m2/24h belinostat, grade 3 HTN and grade 4 pneumonitis were observed. At the MTD of 600 mg/m2/24h belinostat, DLT was seen in 1 of 6 pts; however, all 6 pts required later dose reductions. We thus considered 500 mg/m2/24h in combination with Cis and Etop to be the recommended Phase II dose; confirmation ongoing. PKs show belinostat levels at 1 uM over the 48h infusion, decreasing rapidly to the 60h timepoint. In total 11 pts, 3 with SCLC, completed 6 cycles. PR was seen in 6 pts (3 with SCLC). PD studies confirmed γH2AX staining in PBMCs and hair follicles, peaking at 36h and 60h, respectively. Tubulin and lysine acetylation (Ac-K) in PBMCs peaked at 36h; Ac-K recovered more rapidly than tubulin, mirroring γH2AX. Conclusions: The MTD of belinostat over 48h by CIV was 600 mg/m2/24h, in combination with Cis 60 mg/m2 on day 1 and Etop 80 mg/m2 on days 1 - 3. PD endpoints indicate that belinostat is active in promoting both acetylation and DNA damage. The HDI combined with chemotherapy requires dose reduction and likely represents an on-target increase in DNA damage. Clinical trial information: NCT00926640.

Phase I trial of bortezomib (PS-341; NSC 681239) and alvocidib (flavopiridol; NSC 649890) in patients with recurrent or refractory B-cell neoplasms

PURPOSE

A phase I study was conducted to determine the dose-limiting toxicities (DLT) and maximum tolerated dose (MTD) for the combination of bortezomib and alvocidib in patients with B-cell malignancies (multiple myeloma, indolent lymphoma, and mantle cell lymphoma).

EXPERIMENTAL DESIGN

Patients received bortezomib by intravenous push on days 1, 4, 8, and 11. Patients also received alvocidib on days 1 and 8 by 30-minute bolus infusion followed by a 4-hour continuous infusion. Treatment was on a 21-day cycle, with indefinite continuation for patients experiencing responses or stable disease. Dose escalation employed a standard 3 + 3 design until the MTD was identified on the basis of DLTs. Pharmacokinetic studies and pharmacodynamic studies were conducted.

RESULTS

Sixteen patients were treated. The MTD was established as 1.3 mg/m(2) for bortezomib and 30 mg/m(2) for alvocidib (both the 30-minute bolus and 4-hour infusions). Common hematologic toxicities included leukopenia, lymphopenia, neutropenia, and thrombocytopenia. Common nonhematologic toxicities included fatigue and febrile neutropenia. DLTs included fatigue, febrile neutropenia, and elevated aspartate aminotransferase (AST) levels. Two complete responses (CR; 12%) and five partial responses (PR; 31%) were observed at the MTD (overall response rate = 44%). Pharmacokinetic results were typical for alvocidib and pharmacodynamic studies yielded variable results.

CONCLUSIONS

The combination of bortezomib and alvocidib is tolerable and an MTD has been established for the tested schedule. The regimen appears active in patients with relapsed and/or refractory multiple myeloma or non-Hodgkin's lymphoma, justifying phase II studies to determine the activity of this regimen more definitively.

Romidepsin: a new therapy for cutaneous T-cell lymphoma and a potential therapy for solid tumors

Romidepsin is a histone deacetylase inhibitor (HDI), approved by the US FDA for the treatment of cutaneous T-cell lymphoma (CTCL). Although various mechanisms have been proposed for the activity of HDIs, including induction of genes controlling cell cycle, acetylation of cytoplasmic proteins and direct induction of apoptosis, the mechanism underlying activity of romidepsin and other HDIs in CTCL is not known. Romidepsin induces long-lasting responses. The side-effect profile is similar to that of other HDIs, causing fatigue, nausea and thrombocytopenia. Management of the CTCL population requires vigilence to prevent infection with skin contaminants, and monitoring of potassium and magnesium, electrolytes found to be low in a large proportion of patients. Electrocardiographic (ECG) changes are common but are not associated with myocardial damage. When molecular end points were evaluated in 61 patients enrolled on a Phase II trial with romidepsin, response was associated with persistence of acetylated histone H3, suggesting that drug exposure is important in effective therapy with romidepsin. Future studies will endeavor to identify combination strategies to increase the efficacy both in resistant CTCL and in solid tumors and to identify biomarkers of response that will allow selection of patients most likely to benefit from the therapy.

Arzoxifene, a new selective estrogen receptor modulator for chemoprevention of experimental breast cancer

Arzoxifene ([6-hydroxy-3-[4-[2-(1-piperidinyl)-ethoxy]phenoxy]-2-(4-methoxyphenyl)]benzo[b]thiophene) is a selective estrogen receptor modulator (SERM) that is a potent estrogen antagonist in mammary and uterine tissue while acting as an estrogen agonist to maintain bone density and lower serum cholesterol. Arzoxifene is a highly effective agent for prevention of mammary cancer induced in the rat by the carcinogen nitrosomethylurea and is significantly more potent than raloxifene in this regard. Arzoxifene is devoid of the uterotrophic effects of tamoxifen, suggesting that, in contrast to tamoxifen, it is unlikely that the clinical use of arzoxifene will increase the risk of developing endometrial carcinoma.

Retinoids increase cell-cell adhesion strength, beta-catenin protein stability, and localization to the cell membrane in a breast cancer cell line: a role for serine kinase activity

In this study we show that a breast cancer cell line (SKBR3) that expresses no E-cadherin and very low levels of beta-catenin protein and exhibits a poorly adhesive phenotype in Matrigel responds to retinoic acid (RA) by a marked increase in epithelial differentiation. Specifically, treatment of cells with all-trans-RA, 9-cis-RA, or a RA receptor alpha-specific ligand resulted in a large increase in cell-cell adhesive strength and stimulated the formation of fused cell aggregates in Matrigel. A retinoid X receptor-specific ligand was ineffective. Exposure of cells to 9-cis-RA for as little as 4 h was sufficient to maintain the adhesive phenotype for at least 4 days. The effects of 9-cis-RA required protein and RNA synthesis, but were not mediated by factors secreted by stimulated cells or by direct cell contact and did not require serum. These 9-cis-RA-induced morphological effects were completely reversed by growing cells in 50 microM Ca2+, suggesting a mechanism involving a 9-cis-RA-induced increase in Ca(2+)-dependent adhesion. Consistent with this, beta-catenin protein levels were markedly elevated in the 9-cis-RA-treated cells, and beta-catenin became localized to a Triton-insoluble pool at regions of cell-cell contact. No change could be detected in beta-catenin steady state messenger RNA levels, but 9-cis-RA did increase beta-catenin protein stability. Treatment of cells with low calcium medium did not prevent the 9-cis-RA-induced increase in total beta-catenin protein, but did prevent its movement to a Triton-insoluble pool at the cell membrane. Among several kinase inhibitors, only the broad spectrum kinase inhibitor staurosporine and the protein kinase C inhibitor bisindoylmaleimide reversed the morphological changes induced by 9-cis-RA. Like treatment with low calcium medium, these inhibitors did not prevent the 9-cis-RA-induced increase in total beta-catenin protein levels, but completely prevented the movement of beta-catenin to the cell membrane. These results point to a role for beta-catenin and serine kinase activity in mediating the action of 9-cis-RA in epithelial differentiation.