CSF1 receptor inhibition of tenosynovial giant cell tumor using novel disease-specific MRI measures of tumor burden.

Aim: Monitoring treatment of tenosynovial giant cell tumor (TGCT) is complicated by the irregular shape and asymmetrical growth of the tumor. We compared responses to pexidartinib by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 with those by tumor volume score (TVS) and modified RECIST (m-RECIST). Materials & methods: MRIs acquired every two cycles were assessed centrally using RECIST 1.1, m-RECIST and TVS and tissue damage score (TDS). Results: Thirty-one evaluable TGCT patients were treated with pexidartinib. From baseline to last visit, 94% of patients (29/31) showed a decrease in tumor size (median change: -60% [RECIST], -66% [m-RECIST], -79% [TVS]). All methods showed 100% disease control rate. For TDS, improvements were seen in bone erosion (32%), bone marrow edema (58%) and knee effusion (46%). Conclusion: TVS and m-RECIST offer potentially superior alternatives to conventional RECIST for monitoring disease progression and treatment response in TGCT. TDS adds important information about joint damage associated with TGCT.

Pexidartinib versus placebo for advanced tenosynovial giant cell tumour (ENLIVEN): a randomised phase 3 trial.

BACKGROUND: Tenosynovial giant cell tumour (TGCT), a rare, locally aggressive neoplasm, overexpresses colony-stimulating factor 1 (CSF1). Surgery is standard with no approved systemic therapy. We aimed to evaluate pexidartinib, a CSF1 receptor inhibitor, in patients with TGCT to provide them with a viable systemic treatment option, especially in cases that are not amenable to surgical resection. METHODS: This phase 3 randomised trial had two parts. Part one was a double-blind study in which patients with symptomatic, advanced TGCT for whom surgery was not recommended were randomly assigned via an integrated web response system (1:1) to the pexidartinib or placebo group. Individuals in the pexidartinib group received a loading dose of 1000 mg pexidartinib per day orally (400 mg morning; 600 mg evening) for the first 2 weeks, followed by 800 mg per day (400 mg twice a day) for 22 weeks. Part two was an open-label study of pexidartinib for all patients. The primary endpoint, assessed in all intention-to-treat patients, was overall response at week 25, and was centrally reviewed by RECIST, version 1.1. Safety was analysed in all patients who received at least one dose of the study drug. This study is registered with ClinicalTrials.gov, number NCT02371369. FINDINGS: Between May 11, 2015, and Sept 30, 2016, of 174 patients assessed for eligibility, 120 patients were randomly assigned to, and received, pexidartinib (n=61) or placebo (n=59). There were 11 dropouts in the placebo group and nine in the pexidartinib group. Emergence of mixed or cholestatic hepatotoxicity caused the data monitoring committee to stop enrolment six patients short of target. The proportion of patients who achieved overall response was higher for pexidartinib than placebo at week 25 by RECIST (24 [39%] of 61 vs none of 59; absolute difference 39% [95% CI 27-53]; p<0·0001). Serious adverse events occurred in eight (13%) of 61 patients in the pexidartinib group and one (2%) of 59 patients in the placebo group. Hair colour changes (67%), fatigue (54%), aspartate aminotransferase increase (39%), nausea (38%), alanine aminotransferase increase (28%), and dysgeusia (25%) were the most frequent pexidartinib-associated adverse events. Three patients given pexidartinib had aminotransferase elevations three or more times the upper limit of normal with total bilirubin and alkaline phosphatase two or more times the upper limit of normal indicative of mixed or cholestatic hepatotoxicity, one lasting 7 months and confirmed by biopsy. INTERPRETATION: Pexidartinib is the first systemic therapy to show a robust tumour response in TGCT with improved patient symptoms and functional outcomes; mixed or cholestatic hepatotoxicity is an identified risk. Pexidartinib could be considered as a potential treatment for TGCT associated with severe morbidity or functional limitations in cases not amenable to improvement with surgery. FUNDING: Daiichi Sankyo.

Structure-Guided Blockade of CSF1R Kinase in Tenosynovial Giant-Cell Tumor.

BACKGROUND: Expression of the colony-stimulating factor 1 (CSF1) gene is elevated in most tenosynovial giant-cell tumors. This observation has led to the discovery and clinical development of therapy targeting the CSF1 receptor (CSF1R). METHODS: Using x-ray co-crystallography to guide our drug-discovery research, we generated a potent, selective CSF1R inhibitor, PLX3397, that traps the kinase in the autoinhibited conformation. We then conducted a multicenter, phase 1 trial in two parts to analyze this compound. In the first part, we evaluated escalations in the dose of PLX3397 that was administered orally in patients with solid tumors (dose-escalation study). In the second part, we evaluated PLX3397 at the chosen phase 2 dose in an extension cohort of patients with tenosynovial giant-cell tumors (extension study). Pharmacokinetic and tumor responses in the enrolled patients were assessed, and CSF1 in situ hybridization was performed to confirm the mechanism of action of PLX3397 and that the pattern of CSF1 expression was consistent with the pathological features of tenosynovial giant-cell tumor. RESULTS: A total of 41 patients were enrolled in the dose-escalation study, and an additional 23 patients were enrolled in the extension study. The chosen phase 2 dose of PLX3397 was 1000 mg per day. In the extension study, 12 patients with tenosynovial giant-cell tumors had a partial response and 7 patients had stable disease. Responses usually occurred within the first 4 months of treatment, and the median duration of response exceeded 8 months. The most common adverse events included fatigue, change in hair color, nausea, dysgeusia, and periorbital edema; adverse events rarely led to discontinuation of treatment. CONCLUSIONS: Treatment of tenosynovial giant-cell tumors with PLX3397 resulted in a prolonged regression in tumor volume in most patients. (Funded by Plexxikon; ClinicalTrials.gov number, NCT01004861.).

Peginesatide for anemia in patients with chronic kidney disease not receiving dialysis.

BACKGROUND: Peginesatide is a peptide-based erythropoiesis-stimulating agent (ESA) that may have therapeutic potential for anemia in patients with advanced chronic kidney disease. We evaluated the safety and efficacy of peginesatide, as compared with another ESA, darbepoetin, in 983 such patients who were not undergoing dialysis. METHODS: In two randomized, controlled, open-label studies (PEARL 1 and 2), patients received peginesatide once a month, at a starting dose of 0.025 mg or 0.04 mg per kilogram of body weight, or darbepoetin once every 2 weeks, at a starting dose of 0.75 µg per kilogram. Doses of both drugs were adjusted to achieve and maintain hemoglobin levels between 11.0 and 12.0 g per deciliter for 52 weeks or more. The primary efficacy end point was the mean change from the baseline hemoglobin level to the mean level during the evaluation period; noninferiority was established if the lower limit of the two-sided 97.5% confidence interval was -1.0 g per deciliter or higher. Cardiovascular safety was evaluated on the basis of an adjudicated composite end point. RESULTS: In both studies and at both starting doses, peginesatide was noninferior to darbepoetin in increasing and maintaining hemoglobin levels. The mean differences in the hemoglobin level with peginesatide as compared with darbepoetin in PEARL 1 were 0.03 g per deciliter (97.5% confidence interval [CI], -0.19 to 0.26) for the lower starting dose of peginesatide and 0.26 g per deciliter (97.5% CI, 0.04 to 0.48) for the higher starting dose, and in PEARL 2 they were 0.14 g per deciliter (97.5% CI, -0.09 to 0.36) and 0.31 g per deciliter (97.5% CI, 0.08 to 0.54), respectively. The hazard ratio for the cardiovascular safety end point was 1.32 (95% CI, 0.97 to 1.81) for peginesatide relative to darbepoetin, with higher incidences of death, unstable angina, and arrhythmia with peginesatide. CONCLUSIONS: The efficacy of peginesatide (administered monthly) was similar to that of darbepoetin (administered every 2 weeks) in increasing and maintaining hemoglobin levels. However, cardiovascular events and mortality were increased with peginesatide in patients with chronic kidney disease who were not undergoing dialysis. (Funded by Affymax and Takeda Pharmaceutical; ClinicalTrials.gov numbers, NCT00598273 [PEARL 1], NCT00598442 [PEARL 2], NCT00597753 [EMERALD 1], and NCT00597584 [EMERALD 2].).

Randomized Trial on the Effect of an Oral Spleen Tyrosine Kinase Inhibitor in the Treatment of IgA Nephropathy.

Introduction: We reported increased spleen tyrosine kinase (SYK) expression in kidney biopsies of patients with IgA nephropathy (IgAN) and that inhibition of SYK reduces inflammatory cytokines production from IgA stimulated mesangial cells. Methods: This study was a double-blind, randomized, placebo-controlled phase 2 trial of fostamatinib (an oral SYK inhibitor) in 76 patients with IgAN. Patients were randomized to receive placebo, fostamatinib at 100 mg or 150 mg twice daily for 24 weeks on top of maximum tolerated dose of renin-angiotensin system inhibitors. The primary end point was reduction of proteinuria. Secondary end points included change from baseline in estimated glomerular filtration rate (eGFR) and kidney histology. Results: Although we could not detect significant reduction in proteinuria with fostamatinib overall, in a predetermined subgroup analysis, there was a trend for dose-dependent reduction in median proteinuria (from baseline to 24 weeks by 14%, 27%, and 36% in the placebo, fostamatinib 100 mg, and 150 mg groups, respectively) in patients with baseline urinary protein-to-creatinine ratios (UPCR) more than 1000 mg/g. Kidney function (eGFR) remained stable in all groups. Fostamatinib was well-tolerated. Side effects included diarrhea, hypertension, and increased liver enzymes. Thirty-nine patients underwent repeat biopsy showing reductions in SYK staining associated with therapy at low dose (-1.5 vs. 1.7 SYK+ cells/glomerulus in the placebo group, P < 0.05). Conclusions: There was a trend toward reduction in proteinuria with fostamatinib in a predefined analysis of high risk patients with IgAN despite maximal care, as defined by baseline UPCR greater than 1000 mg/g. Further study may be warranted.

Results from Phase I Extension Study Assessing Pexidartinib Treatment in Six Cohorts with Solid Tumors including TGCT, and Abnormal CSF1 Transcripts in TGCT.

PURPOSE: To assess the response to pexidartinib treatment in six cohorts of adult patients with advanced, incurable solid tumors associated with colony-stimulating factor 1 receptor (CSF1R) and/or KIT proto-oncogene receptor tyrosine kinase activity. PATIENTS AND METHODS: From this two-part phase I, multicenter study, pexidartinib, a small-molecule tyrosine kinase inhibitor that targets CSF1R, KIT, and FMS-like tyrosine kinase 3 (FLT3), was evaluated in six adult patient cohorts (part 2, extension) with advanced solid tumors associated with dysregulated CSF1R. Adverse events, pharmacokinetics, and tumor responses were assessed for all patients; patients with tenosynovial giant cell tumor (TGCT) were also evaluated for tumor volume score (TVS) and patient-reported outcomes (PRO). CSF1 transcripts and gene expression were explored in TGCT biopsies. RESULTS: Ninety-one patients were treated: TGCT patients (n = 39) had a median treatment duration of 511 days, while other solid tumor patients (n = 52) had a median treatment duration of 56 days. TGCT patients had response rates of 62% (RECIST 1.1) and 56% (TVS) for the full analysis set. PRO assessments for pain showed improvement in patient symptoms, and 76% (19/25) of TGCT tissue biopsy specimens showed evidence of abnormal CSF1 transcripts. Pexidartinib treatment of TGCT resulted in tumor regression and symptomatic benefit in most patients. Pexidartinib toxicity was manageable over the entire study. CONCLUSIONS: These results offer insight into outcome patterns in cancers whose biology suggests use of a CSF1R inhibitor. Pexidartinib results in tumor regression in TGCT patients, providing prolonged control with an acceptable safety profile.