Silent infarcts in young children with sickle cell disease.

Silent infarcts have been reported most commonly in school-aged children with homozygous sickle cell disease (SCD-SS) and are associated with neurocognitive deficits. However, the prevalence of silent infarcts in younger children with SCD-SS is not well defined. In this retrospective study, brain magnetic resonance imaging and angiography (MRI/A) studies performed before 6 years of age in a cohort of children with SCD-SS were analysed and the prevalence of abnormalities was calculated. Clinical and laboratory parameters were compared between the groups with and without silent infarcts. Sixty-eight of 96 children in the cohort had brain MRI/A performed prior to age 6 years. Of the 65 who were neurologically asymptomatic, 18 (27.7%, 95% CI 17.3-40.2%) had silent infarcts (mean age 3.7 +/- 1.1 years, range 1.3-5.9 years). Factors associated with silent infarcts included cerebral vessel stensosis by magnetic resonance angiography, lower rates of vaso-occlusive pain and acute chest syndrome and lower haemoglobin levels. The prevalence of silent infarcts in young children with SCD-SS is similar to that of older children and anaemia and severe vasculopathy may be risk factors.

Phase I study of the effect of gastric acid pH modulators on the bioavailability of oral dasatinib in healthy subjects.

Dasatinib is a tyrosine kinase inhibitor (including BCR-ABL and the SRC family) that is effective in patients with chronic myeloid leukemia. Dasatinib has pH-dependent solubility and is bioavailable as an oral formulation. The effect of gastric pH modifiers on dasatinib pharmacokinetics is evaluated in an open-label, randomized, 3-period, 3-treatment crossover study. Twenty-four healthy subjects receive treatment A (2 doses of dasatinib 50 mg separated by 12 hours), treatment B (famotidine 40 mg given 2 hours after dasatinib 50 mg and 10 hours before another dose of dasatinib 50 mg), and treatment C (30 mL of an antacid containing aluminum/magnesium hydroxides given 2 hours before dasatinib 50 mg and concomitantly with dasatinib 50 mg 12 hours after the previous dasatinib dose); a 7-day washout separates each treatment period. When famotidine is administered 2 hours after dasatinib, dasatinib exposure is similar to dasatinib administered alone. However, dasatinib exposure is reduced by approximately 60% when famotidine is administered 10 hours before dasatinib dosing. In contrast, dasatinib exposure is unchanged when antacid (Maalox) is administered 2 hours before dasatinib; but when the antacid is coadministered with dasatinib, dasatinib exposure is reduced by approximately 55% to 58%. This indicates that H(2)-receptor antagonists should not be coadministered with dasatinib. Dasatinib may be administered with acid-neutralizing antacids if the doses are temporally separated by at least 2 hours.

Metabolism and disposition of dasatinib after oral administration to humans.

SPRYCEL (dasatinib, BMS-354825; Bristol-Myers Squibb, Princeton, NJ), a multiple kinase inhibitor, is currently approved to treat chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia tumors in patients who are resistant or intolerant to imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). After a 100-mg single p.o. dose of [(14)C]dasatinib to healthy volunteers, the radioactivity was rapidly absorbed (T(max) approximately 0.5 h). Both dasatinib and total radioactivity (TRA) plasma concentrations decreased rapidly with elimination half-life values of <4 h. Dasatinib was the major drug-related component in human plasma. At 2 h, dasatinib accounted for 25% of the TRA in plasma, suggesting that metabolites contributed significantly to the total drug-related component. There were many circulating metabolites detected that included hydroxylated metabolites (M20 and M24), an N-dealkylated metabolite (M4), an N-oxide (M5), an acid metabolite (M6), glucuronide conjugates (M8a,b), and products of further metabolism of these primary metabolites. Most of the administered radioactivity was eliminated in the feces (85%). Urine recovery accounted for <4% of the dose. Dasatinib accounted for <1 and 19% of the dose in urine and feces, respectively, suggesting that dasatinib was well absorbed after p.o. administration and extensively metabolized before being eliminated from the body. The exposures of pharmacologically active metabolites M4, M5, M6, M20, and M24 in patients, along with their cell-based IC(50) for Src and Bcr-Abl kinase inhibition, suggested that these metabolites were not expected to contribute significantly toward in vivo activity.

Importance of characterizing determinants of variability in exposure: application to dasatinib in subjects with chronic myeloid leukemia.

Characterizing the key determinants of variability in the exposure of orally administered drugs may be important in understanding the implications of exposure variability on clinical responses. In particular, partitioning overall variability into interoccasion variability (IOV) and interindividual variability (IIV) allows a better assessment of the clinical importance of exposure variability. The IOV characterizes the dose-to-dose variability in exposure within a subject and is likely to be less clinically relevant than IIV for chronically administered drugs as the effect of IOV averages out over repeated dosing. The main aims of this model-based analysis were (1) to characterize the IOV and IIV of dasatinib, a novel, orally administered, multitargeted kinase inhibitor of BCR-ABL and SRC family kinases that is indicated for the treatment of chronic myeloid leukemia and Philadelphia-positive acute lymphoblastic leukemia and (2) to demonstrate using simulated data that it is possible to estimate IIV and IOV in relative bioavailability (F(R)) of an orally administered drug, given an adequate sampling scheme. Variability in dasatinib exposure was estimated to be mainly due to IOV in F(R) (44% coefficient of variation [CV]) and, to a lesser extent, due to IIV in F(R) and IIV in clearance (32% and 25% CV, respectively). The IIV is expected to be more clinically relevant than IOV for chronically administered oral drugs such as dasatinib, as the overall variability in cumulative exposure will be mainly due to IIV. The analysis of simulated data demonstrated that models ignoring either IIV or IOV in F(R) resulted in upwardly biased estimates of interindividual or residual variability. Thus, it may be important to account for both IIV and IOV in F(R), particularly for orally administered agents that exhibit absorption-related variability in exposure.

Dasatinib (BMS-354825) pharmacokinetics and pharmacodynamic biomarkers in animal models predict optimal clinical exposure.

PURPOSE: Chronic myeloid leukemia (CML) is caused by reciprocal translocation between chromosomes 9 and 22, forming BCR-ABL, a constitutively activated tyrosine kinase. Imatinib mesylate, a selective inhibitor of BCR-ABL, represents current frontline therapy for CML; however, emerging evidence suggests that drug resistance to imatinib may limit its long-term success. To improve treatment options, dasatinib (BMS-354825) was developed as a novel, oral, multi-targeted kinase inhibitor of BCR-ABL and SRC family kinases. To date, dasatinib has shown promising anti-leukemic activity in preclinical models of CML and in phase I/II clinical studies in patients with imatinib-resistant or imatinib-intolerant disease. EXPERIMENTAL DESIGN: The pharmacokinetic and pharmacodynamic biomarkers of dasatinib were investigated in K562 human CML xenografts grown s.c. in severe combined immunodeficient mice. Tumoral levels of phospho-BCR-ABL/phospho-CrkL were determined by Western blot. RESULTS: Following a single oral administration of dasatinib at a preclinical efficacious dose of 1.25 or 2.5 mg/kg, tumoral phospho-BCR-ABL/phospho-CrkL were maximally inhibited at approximately 3 hours and recovered to basal levels by 24 hours. The time course and extent of the inhibition correlated with the plasma levels of dasatinib in mice. Pharmacokinetic/biomarker modeling predicted that the plasma concentration of dasatinib required to inhibit 90% of phospho-BCR-ABL in vivo was 10.9 ng/mL in mice and 14.6 ng/mL in humans, which is within the range of concentrations achieved in CML patients who responded to dasatinib treatment in the clinic. CONCLUSIONS: Phospho-BCR-ABL/phospho-CrkL are likely to be useful clinical biomarkers for the assessment of BCR-ABL kinase inhibition by dasatinib.

Nivolumab Versus Docetaxel in Previously Treated Patients With Advanced Non-Small-Cell Lung Cancer: Two-Year Outcomes From Two Randomized, Open-Label, Phase III Trials (CheckMate 017 and CheckMate 057).

Purpose Nivolumab, a programmed death-1 inhibitor, prolonged overall survival compared with docetaxel in two independent phase III studies in previously treated patients with advanced squamous (CheckMate 017; ClinicalTrials.gov identifier: NCT01642004) or nonsquamous (CheckMate 057; ClinicalTrials.gov identifier: NCT01673867) non-small-cell lung cancer (NSCLC). We report updated results, including a pooled analysis of the two studies. Methods Patients with stage IIIB/IV squamous (N = 272) or nonsquamous (N = 582) NSCLC and disease progression during or after prior platinum-based chemotherapy were randomly assigned 1:1 to nivolumab (3 mg/kg every 2 weeks) or docetaxel (75 mg/m2 every 3 weeks). Minimum follow-up for survival was 24.2 months. Results Two-year overall survival rates with nivolumab versus docetaxel were 23% (95% CI, 16% to 30%) versus 8% (95% CI, 4% to 13%) in squamous NSCLC and 29% (95% CI, 24% to 34%) versus 16% (95% CI, 12% to 20%) in nonsquamous NSCLC; relative reductions in the risk of death with nivolumab versus docetaxel remained similar to those reported in the primary analyses. Durable responses were observed with nivolumab; 10 (37%) of 27 confirmed responders with squamous NSCLC and 19 (34%) of 56 with nonsquamous NSCLC had ongoing responses after 2 years' minimum follow-up. No patient in either docetaxel group had an ongoing response. In the pooled analysis, the relative reduction in the risk of death with nivolumab versus docetaxel was 28% (hazard ratio, 0.72; 95% CI, 0.62 to 0.84), and rates of treatment-related adverse events were lower with nivolumab than with docetaxel (any grade, 68% v 88%; grade 3 to 4, 10% v 55%). Conclusion Nivolumab provides long-term clinical benefit and a favorable tolerability profile compared with docetaxel in previously treated patients with advanced NSCLC.

Phase 1 pharmacokinetic and drug-interaction study of dasatinib in patients with advanced solid tumors.

BACKGROUND: The recently developed the Src and Abelson (Abl) kinase inhibitor dasatinib has antitumor effects in epithelial and mesenchymal tumors. Preclinical data have indicated that dasatinib is metabolized primarily through cytochrome P450 3A4 (CYP3A4) and may cause QT prolongation. In light of its improved tolerability, the authors were interested in the safety of a once-daily dasatinib regimen. METHODS: The authors conducted a phase 1 trial of dasatinib in 29 patients with advanced solid tumors. Segment 1 of the trial was short term and sequential and was designed to determine whether the coadministration of the potent CYP3A4 inhibitor ketoconazole had an effect on the pharmacokinetics of dasatinib. Segment 2 was designed to evaluate the safety of dasatinib as dosing was increased. QT intervals were monitored closely in both segments. Efficacy was assessed in Segment 2 using both positron emission tomography and computed tomography. RESULTS: Hematologic toxicities were markedly less than those observed in patients with leukemia, whereas nonhematologic toxicities were similar. The authors determined that the maximum recommended dose was 180 mg once daily based on the incidence of pleural effusion. Coadministration of ketoconazole led to a marked increase in dasatinib exposure, which was correlated with an increase in corrected QT (QTc) values of approximately 6 msec. No adverse cardiac events were observed. CONCLUSIONS: The dose-limiting toxic effect for dasatinib was pleural effusion. The pharmacokinetic and cardiac studies indicated that coadministration of dasatinib with potent CYP3A4 inhibitors or agents that prolong the QTc interval should be avoided if possible. Close monitoring for toxicity and dose reduction should be considered if the coadministration of such agents cannot be avoided.

Identification and validation of phospho-SRC, a novel and potential pharmacodynamic biomarker for dasatinib (SPRYCEL), a multi-targeted kinase inhibitor.

PURPOSE: Dasatinib (BMS-354825) is a potent, oral multi-targeted kinase inhibitor. It is an effective therapy for patients with imatinib-resistant or -intolerant Ph+ leukemias,. It has demonstrated promising preclinical anti-tumor activity, and is under clinical evaluation in solid tumors. To support the clinical development of dasatinib, we identified a pharmacodynamic biomarker to assess in vivo SRC kinase inhibition, with subsequent evaluation in cancer patients. METHODS: The biomarker, phosphorylated SRC (phospho-SRC), was first identified in human prostate PC-3 tumor cells and peripheral blood mononuclear cells (PBMCs) in vitro. It was further assessed in nude mice bearing PC-3 xenografts. Phospho-SRC[pY418] in tumors and PBMC were measured by western blot analysis, and were quantified by ELISA assays. Dasatinib plasma concentrations were determined using LC/MS/MS. RESULTS: In PC-3 cells, dasatinib showed dose-dependent anti-proliferative effect, which correlated with the inhibition of phospho-SRC[pY418] and of SRC kinase activity. With a single oral dose of 50 or 15 mg/kg, tumoral phospho-SRC[pY418] was maximally inhibited at 3 h, partially reversed between 7 and 17 h, and completely recovered after 24 h post dose. At 5 mg/kg, tumoral phospho-SRC[pY418] inhibition was less pronounced and recovered more rapidly to baseline level within 24h. Dasatinib (1 mg/kg) resulted in little inhibition. In PBMCs, a similar time course and extent of phospho-SRC[pY418] inhibition was observed. Inhibition of phospho-SRC[pY418] in vivo appeared to correlate with the preclinical in vivo efficacy and PK profiles of dasatinib in mice. CONCLUSIONS: Phospho-SRC[pY418] may potentially be used as a biomarker to enable assessment of target inhibition in clinical studies exploring dasatinib antitumor activity.

Prolongation of the prothrombin time and activated partial thromboplastin time in children with sickle cell disease.

BACKGROUND: Patients with sickle cell disease (SCD) have high rates of perioperative complications, including bleeding 1,2. PROCEDURES: We conducted a retrospective review of pre-operative coagulation studies in pediatric patients with SCD followed by a prospective study of 100 well children with SCD to determine the prevalence of abnormal coagulation screening tests, and to evaluate potential etiologies. RESULTS: In the retrospective study, 32/84 (38.1%) had a prolonged prothrombin time (PT), compared to 8/100 in the prospective study. Prolongations of the activated partial thromboplastin time (aPTT) were less common. Children in the prospective study with prolonged PTs had significantly lower levels of Factor V and VII compared to those with normal PTs. Factor VII levels were <50% in 4/8 with long PTs, compared to 3/92 with normal PTs, P=0.001. Though retrospectively, several patients had normalization of their PT with vitamin K, there was no laboratory evidence of vitamin K deficiency in the prospective study. In the retrospective analysis, six of seven children who had pre-operative coagulation studies and significant intraoperative blood loss had prolonged PTs (P=0.04). CONCLUSIONS: Children with SCD admitted for surgical procedures were more likely to have prolonged PTs than those tested at a well visit. There was intra-patient variability in coagulation studies that may be related to clinical status, hepatocellular dysfunction, and/or increased clotting factor consumption. Future well-designed prospective studies to determine whether abnormal coagulation studies are associated with an increased risk of perioperative bleeding in children with SCD are necessary.

Predicting sentinel node status in AJCC stage I/II primary cutaneous melanoma.

BACKGROUND: Sentinel lymph node (SLN) status is an important prognostic factor for survival for patients with primary cutaneous melanoma. To address the issue of selecting patients at high and low risk for a positive SLN, prognostic factors were sought that predict SLN involvement by examining characteristics of both the primary tumor and the patient within the context of a biological model of melanoma progression. METHODS: The study included 682 patients with primary vertical growth phase (VGP) melanoma and no clinical evidence of metastatic disease who underwent SLN biopsy (1995-2003). Logistic regression and classification tree analyses were used to investigate the association between SLN positivity and Breslow thickness, Clark level, tumor infiltrating lymphocytes (TIL), ulceration, mitotic rate (MR), lesion site, gender, and age. RESULTS.: In all, 88 of the 682 patients had > or =1 positive SLN (12.9%). In the multivariate analysis, MR, TIL, and thickness were found to be independent prognostic factors for SLN positivity. In the classification tree, four different risk groups were defined, ranging from minimal risk (2.1%) to high risk (40.4%). In lesions < r =2.0 mm, MR was important in risk-stratifying patients, and in lesions >2.0 mm TIL was important. CONCLUSIONS: By incorporating biologically based variables such as VGP, TIL, and MR along with thickness into a prognostic model, both patients at high risk and minimal risk for SLN positivity can be identified. If validated, this model can be used in patient management and trial design to select patients to undergo or be spared SLN biopsy.