Safety and efficacy of the combination of sonidegib and ruxolitinib in myelofibrosis: a phase 1b/2 dose-finding study.

The sonidegib and ruxolitinib combination was assessed in an open-label study in JAK inhibitor-naive patients with myelofibrosis (MF). The primary objective of phase 1b was to establish the maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) and phase 2 was to assess spleen volume reduction at weeks 24 and 48. Fifty patients were enrolled. In the dose-escalation phase (n = 23), doses for sonidegib once daily/ruxolitinib twice daily were 400/10 mg (level 1, n = 8), 400/15 mg (level 2, n = 10), and 400/20 mg (level 3, n = 5). Two patients had dose-limiting toxicity at level 2: increased blood creatine phosphokinase (grades 3 and 4, n = 1 each). MTD/RP2D was determined as sonidegib 400 mg daily + ruxolitinib 20 mg twice daily. In phase 1b expansion and phase 2 stage 1 (n = 27), by weeks 24 and 48, ≥35% reduction in spleen volume was observed in 44.4% and 29.6% patients, respectively. By weeks 24 and 48, 42.0% and 26.0% patients had ≥50% reduction in Myelofibrosis Symptom Assessment Form total symptom score, respectively. Most common treatment-related adverse events (grade 3/4) were increased blood creatine phosphokinase (18%), anemia (14%), and thrombocytopenia (12%). Four deaths were reported due to multiple organ dysfunction syndrome (on-treatment; no relationship with study treatment), acute myeloid leukemia, MF progression, and aspiration pneumonia. Although well tolerated, this combination will not be further developed in MF patients due to modest overall benefit compared with historical ruxolitinib monotherapy. This trial was registered at www.clinicaltrials.gov as #NCT01787552.

Multiple administrations of fluconazole increase plasma exposure to ruxolitinib in healthy adult subjects.

PURPOSE: Ruxolitinib is metabolized by cytochrome P450 (CYP)3A4 and CYP2C9. Dual inhibitors of these enzymes (like fluconazole) lead to increased ruxolitinib exposure relative to a single pathway inhibition of CYP3A4 or CYP2C9. The magnitude of this interaction, previously assessed via physiologically based pharmacokinetic (PBPK) models, was confirmed in an open-label, phase 1 study in healthy subjects. METHODS: The effect of multiple doses (200 mg) of fluconazole on single-dose (10 mg) PK of ruxolitinib was investigated including evaluation of the safety and tolerability. The PK parameters of ruxolitinib alone (reference) were compared to those of ruxolitinib combined with fluconazole (test). The point estimate and corresponding two-sided 90% confidence interval for the difference between means of test and reference parameters were determined. RESULTS: All enrolled subjects (N = 15) completed the study. When coadministered with fluconazole, geometric means of ruxolitinib PK parameters Cmax, AUClast, and AUCinf increased by 47%, 234%, and 232%, respectively, vs ruxolitinib alone. The median Tmax decreased slightly, apparent clearance decreased approximately threefold, and elimination half-life increased approximately 2.5-fold, upon ruxolitinib administration with fluconazole vs ruxolitinib alone. These results were consistent with the prospective predictions from a SimCYP PBPK model. Adverse events (AEs) were reported in six subjects (none were suspected to be related to ruxolitinib); no death or on-treatment serious AE was reported. CONCLUSIONS: Coadministration of ruxolitinib with fluconazole significantly increased ruxolitinib systemic exposure; however, no AEs were attributed to ruxolitinib. Concomitant use of ruxolitinib with fluconazole (dose ≤ 200 mg) may require dose reduction/modification of ruxolitinib.

Cancer-associated transforming growth factor beta type II receptor gene mutant causes activation of bone morphogenic protein-Smads and invasive phenotype.

Transforming growth factor beta (TGFbeta) plays a key role in maintaining tissue homeostasis by inducing cell cycle arrest, differentiation and apoptosis, and ensuring genomic integrity. Furthermore, TGFbeta orchestrates the response to tissue injury and mediates repair by inducing epithelial to mesenchymal transition and by stimulating cell motility and invasiveness. Although loss of the homeostatic activity of TGFbeta occurs early on in tumor development, many advanced cancers have coopted the tissue repair function to enhance their metastatic phenotype. How these two functions of TGFbeta become uncoupled during cancer development remains poorly understood. Here, we show that, in human keratinocytes, TGFbeta induces phosphorylation of Smad2 and Smad3 as well as Smad1 and Smad5 and that both pathways are dependent on the kinase activities of the type I and II TGFbeta receptors (T beta R). Moreover, cancer-associated missense mutations of the T beta RII gene (TGFBR2) are associated with at least two different phenotypes. One type of mutant (TGFBR2(E526Q)) is associated with loss of kinase activity and all signaling functions. In contrast, a second mutant (TGFBR2(R537P)) is associated with high intrinsic kinase activity, loss of Smad2/3 activation, and constitutive activation of Smad1/5. Furthermore, this TGFBR2 mutant endows the carcinoma cells with a highly motile and invasive fibroblastoid phenotype. This activated phenotype is T beta RI (Alk-5) independent and can be reversed by the action of a dual T beta RI and T beta RII kinase inhibitor. Thus, identification of such activated T beta RII receptor mutations in tumors may have direct implications for appropriately targeting these cancers with selective therapeutic agents.

Frequent alterations of Smad signaling in human head and neck squamous cell carcinomas: a tissue microarray analysis.

Head and neck squamous cell carcinoma (HNSCC) ranks as the sixth most frequent cancer worldwide. HNSCC cell lines are typically refractory to transforming growth factor-beta (TGF-beta)-mediated cell cycle arrest. A number of these cell lines carry inactivating mutations of the TGF-beta type II (TbetaR-II) receptor, and fail to phosphorylate receptor-associated Smads, Smad2 and Smad3. In addition, we identified several intragenic mutations of the TbetaR-I gene in a small series of metastatic HNSCC specimens, suggesting that disruptions of TGF-beta signaling might contribute to the development and progression of HNSCC. To test this idea, we have now embarked on a larger scale analysis of the patterns of expression and activation of Smads in 170 HNSCC specimens assembled in tissue microarrays. Smad2 protein was expressed by 99% (95% CI: 96-100%) of tumors. The activated form of Smad2, pSmad2, was expressed in 86% (95% CI: 80-91%) of HNSCC, indicating their ability to survive and proliferate in spite of the presence of bioactive TGF-beta within the tissue microenvironment. In the 24 remaining cases (14%; 95% CI: 9-20%), pSmad2 was not detected in the tumor cells, although it was expressed by surrounding stromal cells and capillaries. In addition, 38 tumors (22%; 95% CI: 16-29%) failed to express Smad4 protein. Thus, we found evidence of loss of TGF-beta/Smad signaling in approximately 15-20% of HNSCC specimens, which is consistent with the phenotype of established human SCC lines. Moreover, we found that these Smad signaling defects were associated with a greater tendency for metastatic spread and regional or distant recurrence of HNSCC. These results indicate that inactivation of TGF-beta/Smad signaling occurs frequently in HNSCC and might have an adverse effect on patient outcome.