Patients
Patients were eligible to participate in the study if they had a histologic or cytologic diagnosis of cancer, progressed on previous therapies and had measurable tumors. Starting with Cohort 3, only patients with relapsed and progressive glioma were eligible for this study. All patients were assessed for radiographic responses using Response Evaluation Criteria in Solid Tumors (RECIST) and, for glioma patients, using Macdonald criteria [11]. All patients had to have an Eastern Cooperative Oncology Group performance status of ≤2. Patients were required to have adequate hematologic, hepatic, and renal function and discontinue all previous therapies for cancer at least 4 weeks prior to study enrollment. Exclusion criteria included medically uncontrolled cardiovascular illness, electrocardiogram anomalies, serious pre-existing medical conditions, and any unapproved therapy.
The study was conducted according to the principles of good clinical practice, applicable laws and regulations, and the Declaration of Helsinki. Each institution’s review board approved the study and all patients signed an informed consent document before study participation.
Study design
Galunisertib was evaluated in a 3-part, multicenter, open-label, nonrandomized, dose-escalation first-in-human Phase I study.
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Part A was a dose escalation study using galunisertib monotherapy administered initially to patients with advanced or metastatic cancer as a daily continuous dosing. Starting with Cohort 3 and for the remainder of the study, patients received galunisertib on an intermittent dose regimen of 14 days on/14 days off for a 28-day cycle.
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Part B was a safety study using galunisertib on an intermittent dose regimen at 160 mg/day (80 mg twice daily [BID]) and 300 mg/day (150 mg BID) in combination with lomustine given once every 6 weeks in patients with recurrent malignant glioma who had previously failed approved treatments.
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Part C was a relative bioavailability (RBA) crossover study conducted at only one center to assess two new formulations (publication in preparation). All patients were then eligible to continue on 300 mg/day dosing. In this part of the study, patients with different tumor histologies were eligible to participate; the majority of patients had glioma. The only results from Part C presented in this publication are the results of the T cell subset examination. Other results will be published elsewhere.
Study objectives
The objectives of this study were to characterize the PK profile of galunisertib monotherapy (Part A) and galunisertib in combination with lomustine (Part B). In addition, the relationship of pSMAD2 to galunisertib exposure was assessed (Part A). Biomarkers in plasma and tissue were sampled at baseline and during treatment to identify possible prognostic or predictive biomarkers.
Treatment
In Part A, galunisertib was given orally BID at doses of 20 mg (40 mg/day), 40 mg (80 mg/day), 80 mg (160 mg/day), 120 (240 mg/day) and 150 mg (300 mg/day). In Part B, patients in Cohort 1 received galunisertib at 160 mg/day on intermittent dosing as defined in Part A. Lomustine 100 to 130 mg/m2 was given orally once every 6 weeks beginning 1 week after initial galunisertib dosing. In Cohort 2, 300 mg/day of galunisertib was given on an intermittent dosing schedule and lomustine as in Cohort 1. In Part C, all patients received 300 mg/day monotherapy of galunisertib.
Bioanalytical methods
Human plasma samples obtained during this study were analyzed at PharmaNet USA, Inc. Princeton, New Jersey, USA. The samples were analyzed for galunisertib levels using 2 validated liquid chromatography with tandem mass spectrometry methods. For the high-range method (PharmaNet USA, Inc. SOP TM.589), the lower limit of quantification was 5.000 ng/mL and the upper limit of quantification was 1000.000 ng/mL. The intra-assay accuracy (% relative error) during validation ranged from 1.800 to 10.222 %. The intra-assay precision (% relative standard deviation) during validation ranged from 3.119 to 18.389 %. Samples above the limit of quantification were diluted to yield results within the calibrated range. Samples below the lower limit of quantification using the high-range method were reanalyzed using the low-range method. For the low-range method (PharmaNet USA, Inc. SOP TM.563), the lower limit of quantification was 0.050 ng/mL and the upper limit of quantification was 10.000 ng/mL. The intra-assay accuracy during validation ranged from −5.080 to −2.000 %. The intra-assay precision during validation ranged from 4.404 to 12.245 %.
Pharmacokinetic methods
All patients who received at least 1 dose of galunisertib and had samples collected were subjected to PK analyses. The PK parameters for galunisertib were computed by standard non-compartmental methods of analysis using Win Nonlin Professional Edition (version 5.3) on a computer that met or exceeded the minimum system requirements for this program with appropriate and validated software. The parameters reported from the non-compartmental analyses included the maximum plasma concentration (Cmax), area under the curve from zero to 24 h (AUC(0–24)), AUC from zero time to infinity (AUC(0-∞)), half-life volume of distribution (Vd) and clearance (CL).
Pharmacodynamics pSMAD2 ELISA
pSMAD2 in peripheral blood mononuclear cells (PBMCs) were assessed by a specific ELISA as previously described [9], in which a rabbit polyclonal antibody recognizing pSMAD2 was used. Total SMAD2 was also assessed and used to normalize the expression of pSMAD2.
Flow cytometry for T cell subsets
Blood samples were obtained and prepared for flow cytometry assessment following the instructions of Quintiles Laboratories (Durham, NC). After red blood cell lysis, cells were stained for CD3+, CD8+, CD4+ and CD4+CD25+ CD127−/LOFoxp3+ and events were collected by flow cytometer per standard Quintiles procedures. All results were reported as absolute cell counts and as percentage of lymphocytes.
Baseline biomarker assessments
Plasma samples were analyzed for PD assessments by using a multi-analyte immunoassay panel (MAIP) (Myriad RBM, Austin, TX). The MAIP measurements included 89 plasma proteins [10]. These proteins were evaluated at baseline and during the first cycle of treatment.
Tumor tissue from the initial pathological diagnosis was obtained and slides for immunohistochemistry (IHC) staining were sent to Ventana (Tucson, AZ). All slides were stained for pSMAD2 (Ser465/467, 138D4, Rabbit mAb) following recommendation by the manufacturer (Cell Signaling, MA).
Genetic mutation assessments (including IDH1/2) were conducted at Foundation Medicine (New York, NY) following previously described sequencing and analysis approach [11]. DNA was extracted, sequenced, and 287 genes assessed for point mutations, short insertions/deletions, copy number alterations, and re-arrangements.
Statistical analyses
A power model was fitted to PK parameter estimates Cmax and AUC(0–24) to assess the extent of dose proportionality. Clinical benefit in this study has been defined as a patient with either a complete response (CR), partial response (PR), and stable disease (SD) ≥6 cycles [8]. MAIP results from plasma samples taken at baseline were compared between patients completing >6 cycles and ≤6 cycles using ANOVA. The analysis included controlling the false discovery rate to 30 % using the Benjamini-Hochberg method. Boxplots showing the distributions at baseline of the potentially prognostic markers are provided. Observed TGF-β-stimulated pSMAD2 (pSMAD2+) in PBMCs was normalized by TGF-β-stimulated tSMAD2 [(tSMAD2+) 0.6[9,10]] prior to determining the minimum normalized pSMAD2+ and calculating percentage inhibition post-baseline for each patient. Baseline and minimum post-baseline values for each patient together with maximum percentage inhibition are presented on a line and scatter plot for each patient in Cohort 3 and summary statistics by time point provided from a standard mixed effects regression model, fitting log normalized pSMAD2+ to the fixed effects of log baseline normalized pSMAD2+, nominal time point, dose and their interaction and patient as a random effect.
No statistical analyses were performed on IHC scores of pSMAD2 in tissue, T cells and lymphocytes. The former are summarized using box whisker plots and the latter are displayed in line and scatter plots.