A phase Ib open-label dose escalation study of the safety, pharmacokinetics, and pharmacodynamics of cobimetinib (GDC-0973) and ipatasertib (GDC-0068) in patients with locally advanced or metastatic solid tumors.

BACKGROUND: This Phase Ib study explored combination dosing of the allosteric MEK1/2 inhibitor cobimetinib and the ATP-competitive pan-AKT inhibitor ipatasertib. METHODS: Patients with advanced solid tumors were enrolled to two dose escalation arms, each using a 3 + 3 design in 28-day cycles. In Arm A, patients received concurrent cobimetinib and ipatasertib on days 1-21. In Arm B, cobimetinib was administered intermittently with ipatasertib for 21 days. Primary objectives evaluated dose-limiting toxicities (DLTs), maximum tolerated doses (MTD), and the recommended Phase II dose (RP2D). Secondary objectives included analysis of pharmacokinetic parameters, MAPK and PI3K pathway alterations, changes in tissue biomarkers, and preliminary anti-tumor efficacy. Expansion cohorts included patients with PTEN-deficient triple-negative breast cancer and endometrial cancer. RESULTS: Among 66 patients who received ≥1 dose of study drug, all experienced an adverse event (AE). Although no DLTs were reported, 6 patients experienced Cycle 1 DLT-equivalent AEs. The most common treatment-related AEs were diarrhea, nausea, vomiting, dermatitis acneiform, and fatigue. Thirty-five (53%) patients experienced drug-related AEs of ≥ grade 3 severity. Cobimetinb/ipatasertib MTDs were 60/200 mg on Arm A and 150/300 mg on Arm B; the latter was chosen as the RP2D. No pharmacokinetic interactions were identified. Biomarker analyses indicated pathway blockade and increases in IFNγ and PD-L1 gene expression following the combination. Three patients with endometrial or ovarian cancer achieved partial response, all with PTEN-low disease and two with tumor also harboring KRAS mutation. CONCLUSION: There was limited tolerability and efficacy for this MEK and AKT inhibitor combination. Nonetheless, pharmacodynamic analyses indicated target engagement and suggest rationale for further exploration of cobimetinib or ipatasertib in combination with other anticancer agents. ClinicalTrials.gov identifier: NCT01562275.

Specific oxylipins enhance vertebrate hematopoiesis via the receptor GPR132.

Epoxyeicosatrienoic acids (EETs) are lipid-derived signaling molecules with cardioprotective and vasodilatory actions. We recently showed that 11,12-EET enhances hematopoietic induction and engraftment in mice and zebrafish. EETs are known to signal via G protein-coupled receptors, with evidence supporting the existence of a specific high-affinity receptor. Identification of a hematopoietic-specific EET receptor would enable genetic interrogation of EET signaling pathways, and perhaps clinical use of this molecule. We developed a bioinformatic approach to identify an EET receptor based on the expression of G protein-coupled receptors in cell lines with differential responses to EETs. We found 10 candidate EET receptors that are expressed in three EET-responsive cell lines, but not expressed in an EET-unresponsive line. Of these, only recombinant GPR132 showed EET-responsiveness in vitro, using a luminescence-based ß-arrestin recruitment assay. Knockdown of zebrafish gpr132b prevented EET-induced hematopoiesis, and marrow from GPR132 knockout mice showed decreased long-term engraftment capability. In contrast to high-affinity EET receptors, GPR132 is reported to respond to additional hydroxy-fatty acids in vitro, and we found that these same hydroxy-fatty acids enhance hematopoiesis in the zebrafish. We conducted structure-activity relationship analyses using both cell culture and zebrafish assays on diverse medium-chain fatty acids. Certain oxygenated, unsaturated free fatty acids showed high activation of GPR132, whereas unoxygenated or saturated fatty acids had lower activity. Absence of the carbon-1 position carboxylic acid prevented activity, suggesting that this moiety is required for receptor activation. GPR132 responds to a select panel of oxygenated polyunsaturated fatty acids to enhance both embryonic and adult hematopoiesis.

Phase Ib study of the MEK inhibitor cobimetinib (GDC-0973) in combination with the PI3K inhibitor pictilisib (GDC-0941) in patients with advanced solid tumors.

Purpose We investigated the combination of the MEK inhibitor, cobimetinib, and the pan-PI3K inhibitor, pictilisib, in an open-label, phase Ib study. Experimental Design Patients with advanced solid tumors were enrolled in 3 dose escalation schedules: (1) both agents once-daily for 21-days-on 7-days-off ("21/7"); (2) intermittent cobimetinib and 21/7 pictilisib ("intermittent"); or (3) both agents once-daily for 7-days-on 7-days-off ("7/7"). Starting doses for the 21/7, intermittent, and 7/7 schedules were 20/80, 100/130, and 40/130 mg of cobimetinib/pictilisib, respectively. Nine indication-specific expansion cohorts interrogated the recommended phase II dose and schedule. Results Of 178 enrollees (dose escalation: n = 98), 177 patients were dosed. The maximum tolerated doses for cobimetinib/pictilisib (mg) were 40/100, 125/180, and not reached, for the 21/7, intermittent, and 7/7 schedules, respectively. Six dose-limiting toxicities included grade 3 (G3) elevated lipase, G4 elevated creatine phosphokinase, and G3 events including fatigue concurrent with a serious adverse event (SAE) of diarrhea, decreased appetite, and SAEs of hypersensitivity and dehydration. Common drug-related adverse events included nausea, fatigue, vomiting, decreased appetite, dysgeusia, rash, and stomatitis. Pharmacokinetic parameters of the drugs used in combination were unaltered compared to monotherapy exposures. Confirmed partial responses were observed in patients with BRAF-mutant melanoma (n = 1) and KRAS-mutant endometrioid adenocarcinoma (n = 1). Eighteen patients remained on study ≥6 months. Biomarker data established successful blockade of MAP kinase (MAPK) and PI3K pathways. The metabolic response rate documented by FDG-PET was similar to that observed with cobimetinib monotherapy. Conclusions Cobimetinib and pictilisib combination therapy in patients with solid tumors had limited tolerability and efficacy.

GDC-0810 Pharmacokinetics and Transporter-Mediated Drug Interaction Evaluation with an Endogenous Biomarker in the First-in-Human, Dose Escalation Study.

GDC-0810 (Cheeti et al., 2018) is an orally bioavailable, selective estrogen receptor (ER) degrader developed to treat ER-positive breast cancer. A first-in-human (FIH) dose escalation phase I study (n = 41) was conducted to characterize the pharmacokinetics (PK) of GDC-0810 and its two major metabolites. GDC-0810 demonstrated linear PK from 100 to 600 mg given once daily. The mean terminal half-life following a single 600 mg dose was approximately 8 hours. Since GDC-0810 is a potent in vitro inhibitor of organic anion transporting polypeptide (OATP) 1B1/3, the kinetic profile of coproporphyrin I (CPI), a promising endogenous biomarker for OATP1B1/3, was analyzed retrospectively in a subset of the plasma samples collected in the same FIH study. CPI exhibited a GDC-0810 dose-dependent increase, suggesting in vivo inhibition of OATP1B transporters. To quantitatively predict the magnitude of OATP1B-mediated drug-drug interactions (DDIs) with pravastatin (a known OATP1B substrate), the in vivo unbound inhibition constant was first estimated using a one-compartment model, and then incorporated to a physiologically based pharmacokinetic model. The model showed some underestimation of the magnitude of the DDI when compared with a clinical DDI study result, while prediction had a relatively large uncertainty due to the small effect size, limited sample size, and variability in CPI kinetics. In conclusion, this study characterized the pharmacokinetic profiles of GDC-0810 in breast cancer patients and demonstrated the utility of CPI in detecting OATP1B-mediated DDIs of a new molecular entity as early as FIH study. SIGNIFICANCE STATEMENT: Endogenous biomarkers of transporters have recently been shown to be promising tools in evaluating the risk of clinical transporter-mediated DDIs. This is the first study to report a pharmacokinetic interaction between an investigational molecule and a transporter biomarker in a first-in-human study. The observed interaction and model-based analysis and the prediction provide important insights on the novel approach to quantitatively predict transporter-mediated DDIs as early as FIH studies in the clinical development.

A first-in-human phase I study to evaluate the MEK1/2 inhibitor, cobimetinib, administered daily in patients with advanced solid tumors.

Objective Cobimetinib, a MEK1/2 inhibitor, was administered to patients with advanced solid tumors to assess safety, pharmacokinetics, pharmacodynamics, and anti-tumor activity. Methods For dose-escalation, a 3 + 3 design was used. Oral cobimetinib was administered once daily on a 21-day on/7-day off (21/7) or a 14-day on/14-day off (14/14) schedule. Serial plasma samples were collected for pharmacokinetic (PK) analysis on Day 1 and at steady state. In expansion stages, patients with RAS or RAF mutant tumors were treated at the maximum tolerated dose (MTD) of the 21/7 or 14/14 schedule. Results Ninety-seven patients received cobimetinib. In the 21/7 dose escalation, 36 patients enrolled in 8 cohorts (0.05 mg/kg-80 mg). Dose-limiting toxicities (DLTs) were Grade 4 hepatic encephalopathy, Grade 3 diarrhea, and Grade 3 rash. In the 14/14 dose escalation, 20 patients enrolled in 4 cohorts (60-125 mg). DLTs were Grade 3 rash and Grade 3 blurred vision associated with presence of reversible subretinal fluid. The MTD was 60 mg on 21/7 schedule and 100 mg on 14/14 schedule. Cobimetinib PK showed dose-proportional increases in exposure. The most frequent adverse events attributed to cobimetinib were diarrhea, rash, fatigue, edema, nausea, and vomiting. In patients treated at the 60-mg (21/7) or 100-mg (14/14) dose, one unconfirmed complete response and 6 confirmed partial responses were observed. All responses occurred in melanoma patients; 6 harbored the BRAF(V600E) mutation. Conclusions Cobimetinib is generally well tolerated and durable responses were observed in BRAF(V600E) mutant melanoma patients. Evaluation of cobimetinib in combination with other therapies is ongoing.

Evaluating the Impact of a Pediatric Inpatient Social Care Program in a Community Hospital.

OBJECTIVES: To evaluate the impact of implementing a stakeholder-informed social risk screening and social service referral system in a community hospital setting. METHODS: We implemented a stakeholder-informed social care program at a community hospital in April 2022. The evaluation included patients aged 0 to 17 years admitted to the pediatric unit between April 2021 and March 2022 (1 year preimplementation) and between April 2022 and March 2023 (1 year postimplementation). For a random subset of 232 preimplementation and 218 postimplementation patients, we performed manual data extraction, documenting program process measures and preliminary effectiveness outcomes. We used χ square and Wilcoxon rank tests to compare outcomes between the preimplementation and postimplementation groups. Multivariable logistic regression was used to assess the preliminary effectiveness of the social care program in identifying social risks. RESULTS: Screening rates were higher in the postimplementation group for nearly all social domains. Compared with preimplementation, the postimplementation group had higher rates of social risks identified (17.4% vs 7.8% [P < .01]: adjusted odds ratio 2.9 [95% confidence interval 1.5-5.5]) on multivariate testing. Social work consults were completed more frequently and earlier for the postimplementation group (13.8.% vs 5.6% [P < .01]) and median (19 hours vs 25 hours [P = .03]), respectively. Rates of communication of social risks in discharge summaries were higher in the postimplementation group (46.8% vs 8.2% [P < .001]). CONCLUSIONS: The implementation of a stakeholder-informed social care program within a community hospital setting led to the increased identification of social risks and social work consultations and improved timeliness of social work consultations and written communication of social risks in discharge summaries for primary care providers.

Absolute bioavailability and effect of formulation change, food, or elevated pH with rabeprazole on cobimetinib absorption in healthy subjects.

Cobimetinib is a potent and highly selective inhibitor of MEK1/2. Since cobimetinib exhibited absorption variability in cancer patients, a series of single-dose studies in healthy subjects were conducted to determine absolute bioavailability and elucidate potential effects of formulation, food, and elevated gastric pH on cobimetinib bioavailability. Three crossover trials were performed with a 20 mg cobimetinib oral dose: absolute bioavailability using a 2 mg intravenous infusion (n = 13), relative bioavailability of tablets versus capsules and food effect (n = 20), and drug interaction with a proton pump inhibitor (20 mg of rabeprazole daily for 5 days prior to cobimetinib administration; n = 20). Absolute bioavailability of cobimetinib was 46.2% (24.2, CV %), likely due to metabolism rather than incomplete absorption. The mean systemic clearance of cobimetinib was low (11.7 L/h [28.2, CV %]). Administration of cobimetinib tablets with a high-fat meal delayed drug absorption (prolonged tmax) but had no statistically significant effect on cobimetinib exposure (Cmax and AUC0-∞). Tablet and capsule formulations of cobimetinib showed comparable exposures. Cobimetinib exhibited delayed absorption (tmax) in the presence of rabeprazole, with no statistically significant effects on drug exposure (Cmax and AUC0-∞) in the fasted state. In conclusion, cobimetinib oral absorption was not affected by change in formulation, food, or elevated gastric pH.

Calmodulin inhibitors improve erythropoiesis in Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is a rare hematopoietic disease characterized by a block in red cell differentiation. Most DBA cases are caused by mutations in ribosomal proteins and characterized by higher than normal activity of the tumor suppressor p53. Higher p53 activity is thought to contribute to DBA phenotypes by inducing apoptosis during red blood cell differentiation. Currently, there are few therapies available for patients with DBA. We performed a chemical screen using zebrafish ribosomal small subunit protein 29 (rps29) mutant embryos that have a p53-dependent anemia and identified calmodulin inhibitors that rescued the phenotype. Our studies demonstrated that calmodulin inhibitors attenuated p53 protein amount and activity. Treatment with calmodulin inhibitors led to decreased p53 translation and accumulation but does not affect p53 stability. A U.S. Food and Drug Administration-approved calmodulin inhibitor, trifluoperazine, rescued hematopoietic phenotypes of DBA models in vivo in zebrafish and mouse models. In addition, trifluoperazine rescued these phenotypes in human CD34+ hematopoietic stem and progenitor cells. Erythroid differentiation was also improved in CD34+ cells isolated from a patient with DBA. This work uncovers a potential avenue of therapeutic development for patients with DBA.

Conditional expression of oncogenic K-ras from its endogenous promoter induces a myeloproliferative disease.

Oncogenic ras alleles are among the most common mutations found in patients with acute myeloid leukemia (AML). Previously, the role of oncogenic ras in cancer was assessed in model systems overexpressing oncogenic ras from heterologous promoters. However, there is increasing evidence that subtle differences in gene dosage and regulation of gene expression from endogenous promoters play critical roles in cancer pathogenesis. We characterized the role of oncogenic K-ras expressed from its endogenous promoter in the hematopoietic system using a conditional allele and IFN-inducible, Cre-mediated recombination. Mice developed a completely penetrant myeloproliferative syndrome characterized by leukocytosis with normal maturation of myeloid lineage cells; myeloid hyperplasia in bone marrow; and extramedullary hematopoiesis in the spleen and liver. Flow cytometry confirmed the myeloproliferative phenotype. Genotypic and Western blot analysis demonstrated Cre-mediated excision and expression, respectively, of the oncogenic K-ras allele. Bone marrow cells formed growth factor-independent colonies in methylcellulose cultures, but the myeloproliferative disease was not transplantable into secondary recipients. Thus, oncogenic K-ras induces a myeloproliferative disorder but not AML, indicating that additional mutations are required for AML development. This model system will be useful for assessing the contribution of cooperating mutations in AML and testing ras inhibitors in vivo.

Heterogeneity and clinical significance of ESR1 mutations in ER-positive metastatic breast cancer patients receiving fulvestrant.

Mutations in ESR1 have been associated with resistance to aromatase inhibitor (AI) therapy in patients with ER+ metastatic breast cancer. Little is known of the impact of these mutations in patients receiving selective oestrogen receptor degrader (SERD) therapy. In this study, hotspot mutations in ESR1 and PIK3CA from ctDNA were assayed in clinical trial samples from ER+ metastatic breast cancer patients randomized either to the SERD fulvestrant or fulvestrant plus a pan-PI3K inhibitor. ESR1 mutations are present in 37% of baseline samples and are enriched in patients with luminal A and PIK3CA-mutated tumours. ESR1 mutations are often polyclonal and longitudinal analysis shows distinct clones exhibiting divergent behaviour over time. ESR1 mutation allele frequency does not show a consistent pattern of increases during fulvestrant treatment, and progression-free survival is not different in patients with ESR1 mutations compared with wild-type patients. ESR1 mutations are not associated with clinical resistance to fulvestrant in this study.

Oncogenic K-ras in mouse models of myeloproliferative disease and acute myeloid leukemia.

Oncogenic N-RAS and K-RAS mutations are among the most frequently detected genetic alterations in patients with acute myeloid leukemia (AML). Recently, the role of oncogenic K-ras in leukemogenesis was investigated in a novel mouse model utilizing interferon (IFN)-inducible, Cre-mediated expression of oncogenic K-ras from its endogenous promoter. Conditional expression of oncogenic K-ras from its endogenous promoter in the hematopoietic system induces a lethal myeloproliferative disease in mice, but not AML, indicating that additional mutations are required for AML development. These results are consistent with a model in which the AML phenotype requires at least two cooperating mutations in the hematopoietic progenitor cells: one promoting proliferation and enhanced cell survival (such as oncogenic ras or a constitutively activated receptor tyrosine kinase) and one associated with impaired differentiation and enhanced immortalization (such as loss-of-function mutations in hematopoietic transcription factors). The model system with oncogenic K-ras provides a versatile platform to test the contribution of cooperating mutations in AML, and the efficacy of Ras pathway inhibitors in vivo.

Dogs are more sensitive to antagonists of inhibitor of apoptosis proteins than rats and humans: a translational toxicokinetic/toxicodynamic analysis.

Inhibitor of apoptosis (IAP) proteins suppress apoptosis and are overexpressed in a variety of cancers. GDC-0152 is a potent and selective IAP antagonist being developed as an anticancer agent. In preclinical safety studies, dogs were particularly sensitive to GDC-0152 showing adverse signs of a tumor necrosis factor alpha (TNF-α) driven systemic inflammatory response, related to cellular IAP degradation and activation of NFκB signaling, at lower exposures compared with rat. In addition, downstream increases in systemic levels of cytokines and chemokines, such as monocyte chemotactic protein-1 (MCP-1), were observed. A semimechanistic population toxicokinetic/toxicodynamic (TK/TD) model incorporating transit compartments was used to fit MCP-1 plasma concentrations from rats or dogs given iv GDC-0152 doses. Estimated TD parameters inferred that lower GDC-0152 plasma concentrations triggered more severe increases in plasma MCP-1 in dogs compared with rats. Human simulations performed using dog TD parameters and human pharmacokinetics predicted 300-2400% increases of MCP-1 in humans at iv doses from 0.76 to 1.48mg/kg. Similar simulations using rat TD parameters suggest little or no change. Patients given iv doses of GDC-0152 up to 1.48mg/kg iv showed no substantial increases in systemic MCP-1 or signs of a severe TNF-α driven systemic inflammatory response. Emerging clinical data reported for other IAP antagonists are consistent with our observations. Taken together, the data suggest dogs are more sensitive to IAP antagonists compared with humans and rats. This study illustrates how TK/TD analysis can be utilized to quantitatively translate and context an identified preclinical safety risk in dogs to humans.

Discovery of a potent small-molecule antagonist of inhibitor of apoptosis (IAP) proteins and clinical candidate for the treatment of cancer (GDC-0152).

A series of compounds were designed and synthesized as antagonists of cIAP1/2, ML-IAP, and XIAP based on the N-terminus, AVPI, of mature Smac. Compound 1 (GDC-0152) has the best profile of these compounds; it binds to the XIAP BIR3 domain, the BIR domain of ML-IAP, and the BIR3 domains of cIAP1 and cIAP2 with K(i) values of 28, 14, 17, and 43 nM, respectively. These compounds promote degradation of cIAP1, induce activation of caspase-3/7, and lead to decreased viability of breast cancer cells without affecting normal mammary epithelial cells. Compound 1 inhibits tumor growth when dosed orally in the MDA-MB-231 breast cancer xenograft model. Compound 1 was advanced to human clinical trials, and it exhibited linear pharmacokinetics over the dose range (0.049 to 1.48 mg/kg) tested. Mean plasma clearance in humans was 9 ± 3 mL/min/kg, and the volume of distribution was 0.6 ± 0.2 L/kg.

Oncogenic K-ras cooperates with PML-RAR alpha to induce an acute promyelocytic leukemia-like disease.

Most patients with acute promyelocytic leukemia (APL) express PML-RAR alpha, the fusion product of t(15;17)(q22;q11.2). Transgenic mice expressing PML-RAR alpha develop APL with long latency, low penetrance, and acquired cytogenetic abnormalities. Based on observations that 4% to 10% of APL patients harbor oncogenic ras mutations, we coexpressed oncogenic K-ras from its endogenous promoter with PML-RAR alpha to generate a short-latency, highly penetrant mouse model of APL. The APL disease was characterized by splenomegaly, leukocytosis, extramedullary hematopoiesis (EMH) in spleen and liver with an increased proportion of immature myeloperoxidase-expressing myeloid forms; transplantability to secondary recipients; and lack of cytogenetic abnormalities. Bone marrow cells showed enhanced self-renewal in vitro. This model establishes a role for oncogenic ras in leukemia pathogenesis and thus validates the oncogenic RAS signaling pathway as a potential target for therapeutic inhibition in leukemia patients. This mouse model should be useful for investigating signaling pathways that promote self-renewal in APL and for testing the in vivo efficacy of RAS signaling pathway inhibitors in conjunction with other targeted therapies such as ATRA (all trans retinoic acid) and arsenic trioxide.