Preclinical pharmacology, antitumor activity, and development of pharmacodynamic markers for the novel, potent AKT inhibitor CCT128930

AKT is frequently deregulated in cancer, making it an attractive anticancer drug target. CCT128930 is a novel ATP-competitive AKT inhibitor discovered using fragment- and structure-based approaches. It is a potent, advanced lead pyrrolopyrimidine compound exhibiting selectivity for AKT over PKA, achieved by targeting a single amino acid difference. CCT128930 exhibited marked antiproliferative activity and inhibited the phosphorylation of a range of AKT substrates in multiple tumor cell lines in vitro, consistent with AKT inhibition. CCT128930 caused a G(1) arrest in PTEN-null U87MG human glioblastoma cells, consistent with AKT pathway blockade. Pharmacokinetic studies established that potentially active concentrations of CCT128930 could be achieved in human tumor xenografts. Furthermore, CCT128930 also blocked the phosphorylation of several downstream AKT biomarkers in U87MG tumor xenografts, indicating AKT inhibition in vivo. Antitumor activity was observed with CCT128930 in U87MG and HER2-positive, PIK3CA-mutant BT474 human breast cancer xenografts, consistent with its pharmacokinetic and pharmacodynamic properties. A quantitative immunofluorescence assay to measure the phosphorylation and total protein expression of the AKT substrate PRAS40 in hair follicles is presented. Significant decreases in pThr246 PRAS40 occurred in CCT128930-treated mouse whisker follicles in vivo and human hair follicles treated ex vivo, with minimal changes in total PRAS40. In conclusion, CCT128930 is a novel, selective, and potent AKT inhibitor that blocks AKT activity in vitro and in vivo and induces marked antitumor responses. We have also developed a novel biomarker assay for the inhibition of AKT in human hair follicles, which is currently being used in clinical trials.

Decreased exposure to sunitinib due to concomitant administration of ifosfamide: results of a phase I and pharmacokinetic study on the combination of sunitinib and ifosfamide in patients with advanced solid malignancies

BACKGROUND

This study aimed to define the maximally tolerated dose (MTD) of sunitinib combined with two different infusion schedules of ifosfamide.

METHODS

Patients with advanced solid tumours, good performance score, good organ function, and no standard therapy available were eligible. Continuous once daily sunitinib, in escalating doses per cohort, was combined with ifosfamide, 9 g m(-2) for 3 days or 6 g m(-2) for 5 days, administered every 3 weeks. Pharmacokinetic (PK) and pharmacodynamic (PD) assessments were performed.

RESULTS

With growth-factor support, the MTD of sunitinib combined with either ifosfamide schedule was 12.5 mg in 32 patients enrolled. Neutropenia-related adverse events were dose-limiting toxicities. Sunitinib did not affect ifosfamide PK. Ifosfamide significantly decreased exposure to sunitinib and increased exposure to its metabolite, SU12662. No consistent changes in PD parameters were observed.

CONCLUSION

With growth-factor support, the MTD of sunitinib with both ifosfamide schedules was 12.5 mg. Ifosfamide produced decreased sunitinib blood levels because of CYP3A induction. As PK interactions cannot explain the relatively low sunitinib doses that can be combined with ifosfamide, synergy in toxicity is likely. Whether this also holds true for anti-tumour activity needs to be further explored.

Preparation and evaluation of self-microemulsifying drug delivery systems (SMEDDS) containing atorvastatin

Atorvastatin is insoluble in aqueous solution and the bioavailability after oral administration is low. Self-microemulsifying drug delivery systems (SMEDDS) containing atorvastatin have been successfully prepared to improve its bioavailability. SMEDDS is a mixture of lipid, surfactant, and cosurfactant, which are emulsified in aqueous medium under gentle digestive motility in the gastrointestinal tract. Pseudo-ternary phase diagrams composed of various excipients were plotted. Droplet size, zeta-potential and long-term physical stability of the formulations were investigated. The release of atorvastatin from SMEDDS capsules was studied using the dialysis bag method in 0.1 m HCl and phosphate buffer (pH 7.4), compared with the release of atorvastatin from a conventional tablet. A pharmacokinetic study was performed in 6 beagle dogs after oral administration of 6 mg kg−1 atorvastatin. The bioavailability of atorvastatin SMEDDS capsules was significantly increased compared with that of the conventional tablet. SMEDDS capsules consisting of Labrafil, propylene glycol and Cremophor RH40 provided the greatest bioavailability. Our studies indicate that the use of SMEDDS for the delivery of atorvastatin can improve its bioavailability.

Phase II study of continuous daily sunitinib dosing in patients with previously treated advanced non-small cell lung cancer

BACKGROUND

Sunitinib malate (SUTENT) has promising single-agent activity given on Schedule 4/2 (4 weeks on treatment followed by 2 weeks off treatment) in advanced non-small cell lung cancer (NSCLC).

METHODS

We examined the activity of sunitinib on a continuous daily dosing (CDD) schedule in an open-label, multicentre phase II study in patients with previously treated, advanced NSCLC. Patients > or =18 years with stage IIIB/IV NSCLC after failure with platinum-based chemotherapy, received sunitinib 37.5 mg per day. The primary end point was objective response rate (ORR). Secondary end points included progression-free survival (PFS), overall survival (OS), 1-year survival rate, and safety.

RESULTS

Of 47 patients receiving sunitinib, one patient achieved a confirmed partial response (ORR 2.1% (95% confidence interval (CI) 0.1, 11.3)) and 11 (23.4%) had stable disease (SD) > or =8 weeks. Five patients had SD>6 months. Median PFS was 11.9 weeks (95% CI 8.6, 14.1) and median OS was 37.1 weeks (95% CI 31.1, 69.7). The 1-year survival probability was 38.4% (95% CI 24.2, 52.5). Treatment was generally well tolerated.

CONCLUSIONS

The safety profile and time-to-event analyses, albeit relatively low response rate of 2%, suggest single-agent sunitinib on a CDD schedule may be a potential therapeutic agent for patients with advanced, refractory NSCLC.

Effects of cyclosporin A and itraconazole on the pharmacokinetics of atorvastatin in rats

AIM

To evaluate the effects of cyclosporin A and itraconazole, which were used as inhibitors of P-glycoprotein (P-gp) and/or cytochrome P450 (CYP) 3A4 on the pharmacokinetics of atorvastatin in rats.

METHODS

The pharmacokinetic parameters of atorvastatin were measured after intravenous (2 mg/kg) and intragastric (10 mg/kg) administration of atorvastatin in rats, which were pretreated with cyclosporin A (5, 10, and 20 mg/kg) or itraconazole (5, 10, and 20 mg/kg).

RESULTS

Compared with the control rats, cyclosporin A and itraconazole altered the pharmacokinetics of atorvastatin significantly. The AUC0-t values of atorvastatin after intragastric administration, pretreated with cyclosporin A (5-20 mg/kg), increased by 32.3%, 61.8%, and 187.2%, respectively, but the CLbile values decreased (P<0.01, 5-20 mg/kg). With pretreatment of itraconazole (5-20 mg/kg), the AUC(0-t) values of atorvastatin increased by 88.2%, 102%, and 123%, respectively, but the CL(bile) values decreased (P<0.01, 5-20 mg/kg).

CONCLUSION

These data indicated that cyclosporin A could be effective in inhibiting the efflux of atorvastatin, and itraconazole could be effective in inhibiting both the metabolism and biliary excretion of atorvastatin.

Advantages of achiral h.p.l.c. as a preparative step for chiral analysis in biological samples and its use in toxicokinetic studies

1. Achiral reverse-phase h.p.l.c. with semi-automated post-column fraction collection and solid-phase sample reconcentration, has been applied as the purification procedure during the enantiomeric quantification of two widely differing experimental drugs; an HMG-CoA reductase inhibitor (I) and an alpha 2-adrenoceptor antagonist (II). 2. The robust and specific achiral methodologies were available prior to the need for chiral analyses and recovery of drug from the fractions provided clean samples from a variety of biological matrices, without the need to develop compatible achiral/chiral mobile phases. 3. Compared with direct chiral chromatography of plasma extracts, this approach decreased the potential for metabolites and endogenous components to interfere or impair the performance of the chiral stationary phase. 4. The availability of quantitative data from achiral analysis of samples negated the need for internal standardization of the chiral analyses, helped confirm assay specificity and provided potential to determine enantiomeric ratios where only one isomer could be accurately measured. 5. Routine enantiomeric analyses were successfully carried out on samples taken from animals dosed orally with the racemic drugs, providing important data on the possible levels of exposure to individual enantiomers during toxicity testing.

Amlodipine/atorvastatin fixed-dose combination: a review of its use in the prevention of cardiovascular disease and in the treatment of hypertension and dyslipidemia

Amlodipine/atorvastatin (Caduet) is a once-daily fixed-dose combination of the dihydropyridine calcium channel antagonist amlodipine and the HMG-CoA reductase inhibitor atorvastatin. In Europe, the combination is indicated for the prevention of cardiovascular events in hypertensive patients with three concomitant cardiovascular risk factors and, in the US, it is indicated for the management of hypertension and dyslipidemia in patients for whom treatment with both agents is appropriate. In clinical trials, the fixed-dose combination of amlodipine/atorvastatin effectively managed two important risk factors simultaneously in hypertensive patients at risk of cardiovascular disease or in those with concomitant hypertension and dyslipidemia. The combination is bioequivalent to amlodipine and atorvastatin given alone and does not modify the efficacy of either single agent. Amlodipine/atorvastatin is generally well tolerated, with a tolerability profile consistent with that of each single agent. Compared with the coadministration of each single agent, the convenience of single-pill amlodipine/atorvastatin has the potential to improve patient adherence and the management of cardiovascular risk in selected patients, thereby improving clinical outcomes.

Introduction to 'A multitargeted approach: clinical advances in the treatment of solid tumours'

Although single-target agents have been shown to improve patient outcomes in certain tumour types, drug resistance often occurs due to salvage pathways that compensate for the inhibited signalling pathway. Simultaneous inhibition of individual target receptors along multiple pathways has been shown to have additive inhibitory effects on tumour growth and vasculature, and data supporting the efficacy of strategies incorporating multitargeted agents in the treatment of several tumour types have already begun to emerge in the clinical setting. This supplement provides an overview of presentations from a satellite symposium that took place at the European Society of Medical Oncology congress on 29 September 2006, entitled 'A Multitargeted Approach: Clinical Advances in the Treatment of Solid Tumours', which discusses the most recent data on multitargeted agents with a focus on sunitinib malate (Sutent, Pfizer Inc.).

Determination of chemically reduced pyrrolobenzodiazepine SJG-136 in human plasma by HPLC-MS/MS: application to an anticancer phase I dose escalation study

SJG-136 1,1'-[[(propane-1,3-diyl)dioxy]bis[(11aS)-7-methoxy-2-methylidene-1,2,3,11a-tetrahydro-5H-pyr- rolo[2,1-c][1,4]benzodiazepin-5-one]] (NSC 694501), is a bifunctional pyrrolobenzodiazepine (PBD) dimer that forms selective, irreversible, interstrand DNA cross-links via exocyclic N2 atoms of two guanine bases, with a preference for 5'PuGATCPy binding sites. SJG-136 is highly cytotoxic in human tumor cells in vitro and in human tumor xenograft models in vivo at subnanomolar concentrations and is currently in anticancer phase I clinical trials in the United Kingdom and United States. To support correlative pharmacokinetics studies, a highly sensitive HPLC-MS/MS assay was developed and validated for the reliable quantitation of SJG-136 in human plasma, using the structurally similar PBD dimer DSB-120 as an internal standard. Chemical reduction of SJG-136 to its corresponding amine (SJG-136-H(4), [M + H](+)m/z 561) improved HPLC peak resolution and sensitivity by minimizing complications that arose from the reactivity of the labile imine moieties. Plasma samples were processed by protein precipitation and centrifugal membrane dialysis; components were separated by HPLC using an Agilent Rapid Resolution HT 1.8 mm (2.1 mm x 50 mm) analytical column. The total analysis time from injection to injection was 11 min. Electrospray MS/MS detection of SJG-136-H(4) was based on the selected reaction monitoring (SRM) transition [M + H](+)m/z 561 --> 301. The analytical response ratio was linearly proportional to the plasma concentration of SJG-136 over the nominal concentration range of 25 pg/ml to 250 ng/ml, with a coefficient of determination of r > or = 0.999. The intrarun absolute %RE was < or =19.6, 14.2, and 14.0% at 0.056, 2.83, and 56.3 ng/ml, respectively. The corresponding %RSD was < or =14.9%, 9.01, and 4.59%. The interday %RSD was < or =2.72, 3.46, and 5.20%. The lower and upper limits of quantitation were 0.056 and 56 ng/ml, respectively; recovery of SJG-136 from plasma was > or = 62% across the validated concentration range. The sensitivity of the validated assay was sufficient to detect SJG-136 in human subjects for up to 6 h after intravenous administration of 6 microg/m(2), the starting dose of an NCI-sponsored dose escalation study.

The genetic determinants of atorvastatin response

The statins or HMG-CoA reductase inhibitors are considered one of the most effective classes of drugs for reducing LDL and total cholesterol. Although, statin treatment has beneficial effects in the prevention of cardiovascular disease, considerable inter-individual variation exists in response to statin therapy, as well as in the incidence of adverse effects. Genetic factors contribute to patients' inter-variability in the lipid-lowering response to statins,drug-interactions and the occurrence of muscle damage havebeen reported. However, studies investigating aspects of pharmacokinetics, pharmacodynamics and disease-related genes have found no association that could impact on the decisions to treat with statins. Improved strategies that assess the simultaneous influence of multiple relevant susceptibility factors on disease risk (eg, diet, lifestyle and gene effects) are required. Data from pharmacogenetics studies investigating the association between gene variation and drug response and/or susceptibility to adverse effects are promising and are expected to impact on the clinical treatment of hypercholesterolemia.

Sorafenib and sunitinib: novel targeted therapies for renal cell cancer

Renal cell cancer (RCC) is a relatively uncommon malignancy, with 51,190 cases expected to be diagnosed in 2007. Localized disease is curable by surgery; however, locally advanced or metastatic disease is not curable in most cases and, until recently, had a limited response to drug treatment. Historically, biologic response modifiers or immunomodulating agents were tested in clinical trials based on observations that some cases of RCC can spontaneously regress. High-dose aldesleukin is approved by the United States Food and Drug Administration as a treatment for advanced RCC; however, the drug is associated with a high frequency of severe adverse effects. Responses have been observed with low-dose aldesleukin and interferon alfa, but with little effect on overall survival. Sorafenib and sunitinib are novel therapies that target growth factor receptors known to be activated by the hypoxia-inducible factor and the Ras-Raf/MEK/ERK pathways. These pathways are important in the pathophysiology of RCC. Sorafenib and sunitinib have shown antitumor activity as first- and second-line therapy in patients with cytokine-refractory metastatic RCC who have clear-cell histology. Although complete responses are not common, both drugs promote disease stabilization and increase progression-free survival. This information suggests that disease stabilization may be an important determinant for response in RCC and possibly other cancers. Sorafenib and sunitinib are generally well tolerated and are considered first- and second-line treatment options for patients with advanced clear cell RCC. In addition, sorafenib and sunitinib have shown promising results in initial clinical trials evaluating antitumor activity in patients who are refractory to other antiangiogenic therapy. The most common toxicities with both sorafenib and sunitinib are hand-foot syndrome, rash, fatigue, hypertension, and diarrhea. Research is directed toward defining the optimal use of these new agents.

P-glycoprotein has differential effects on the disposition of statin acid and lactone forms in mdr1a/b knockout and wild-type mice

In the present study we examined the disposition of atorvastatin, lovastatin, and simvastatin in acid and lactone forms and pravastatin in acid form in multidrug-resistant gene (mdr1a/b) knockout (KO), and wild-type (WT) mice. Each statin was administered s.c. to mdr1a/b KO and WT mice at 3.0 mg/kg (n > or = 3 mice/time point). Blood, brain, and liver samples were harvested at 0, 0.5, 1.5, and 3 h postdose. Plasma and tissue concentrations of the acid and lactone (only the acid form was determined for pravastatin) were determined using a liquid chromatography-mass spectrometry method. Both lactone and acid were observed in plasma when lactones were administered, but only acids were detected when the acid forms were administered. The plasma and liver concentrations of acid or lactone were similar between the KO and WT mice. Two- to 23-fold higher concentrations were observed in liver than in plasma, suggesting potential uptake transporters involved. A significantly higher (p < 0.05) brain penetration in the KO compared with the WT mice was observed for lovastatin acid (but the brain/plasma ratio was low for both KO and WT mice) and lactone and simvastatin lactone but not for atorvastatin or pravastatin. The present results suggest that mouse P-glycoprotein does not affect the lactone-acid interconversion or liver-plasma distribution. Furthermore, P-glycoprotein plays a limited role in restricting the brain penetration of the acid forms of atorvastatin, pravastatin, simvastatin, lovastatin, and atorvastatin lactone but may limit the brain availability of the lactone forms of simvastatin and lovastatin.

Preclinical pharmacology profile of CS-706, a novel cyclooxygenase-2 selective inhibitor, with potent antinociceptive and anti-inflammatory effects

We report here the preclinical anti-inflammatory profile of CS-706 [2-(4-ethoxyphenyl)-4-methyl-1-(4-sulfamoylphenyl)-1H-pyrrole], a novel cyclooxygenase-2 (COX-2) selective inhibitor. CS-706 selectively inhibited COX-2 in a human whole blood assay with an IC(50) of 0.31 microM, compared with an IC(50) of 2.2 microM for COX-1. The selectivity ratio of CS-706 was higher than those of the conventional non-steroidal anti-inflammatory drugs naproxen, indomethacin, and Diclofenac-Na, whereas it was lower than those of rofecoxib, valdecoxib and etoricoxib. It was similar to that of celecoxib. The pharmacokinetic profile of CS-706 showed rapid absorption and dose-proportional exposure after oral administration to rats. CS-706 inhibited prostaglandin E(2) production in inflamed tissue induced by yeast-injection in rats with potency similar to that of indomethacin. However, it inhibited gastric mucosal prostaglandin E(2) production in normal rats weakly compared with indomethacin. CS-706 ameliorated both yeast-induced inflammatory acute pain (ED(50)=0.0090 mg/kg) and adjuvant-induced chronic arthritic pain (ED(50)=0.30 mg/kg) in rats. CS-706 showed more potent antinociceptive activity than celecoxib and rofecoxib in these models. In an adjuvant-induced arthritic model in rats, CS-706 suppressed foot swelling prophylactically with an ID(50) of 0.10 mg/kg/day, and decreased foot swelling in the established arthritis therapeutically in a dose range of 0.040 to 1.0 mg/kg/day. Single administration of up to 100 mg/kg of CS-706 induced no significant gastric lesions in rats. In conclusion, CS-706 is a COX-2-selective inhibitor with a potent antinociceptive and anti-inflammatory activity and a gastric safety profile.

Interaction between a commercially available St. John’s wort product (Movina) and atorvastatin in patients with hypercholesterolemia

OBJECTIVE

The aim of this study was to assess the effect of treatment with a St. John's wort product (Movina) on cholesterol [total cholesterol, low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol] and triglyceride levels in patients with hypercholesterolemia on treatment with a stable dose of atorvastatin in a controlled, randomised, open, crossover interaction study.

METHODS

Sixteen patients with hypercholesterolemia treated with a stable dose of atorvastatin (10-40 mg/daily) for at least 3 months were treated with Movina one tablet (containing 300 mg of hypericum perforatum) twice daily and control (a commercially available multivitamin tablet Vitamineral). After a run-in period of 4 weeks, patients were randomised to treatment with either Movina or control for 4 weeks in a crossover design. The atorvastatin dose was kept unchanged during the study period (12 weeks), and assessments of total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides were performed in the morning with the patients in the fasting condition. The difference between control and active treatment in LDL cholesterol after 4 weeks of treatment was the primary endpoint.

RESULTS

All patients completed the study. The St. John's wort product significantly increased the serum level of LDL cholesterol compared with control (2.66 mmol/l compared with 2.34 mmol/l, p = 0.004). A significant increase in total cholesterol was also observed (5,10 mmol/l compared with 4.78 mmol/l, p = 0.02). No statistically significant change was observed in HDL cholesterol (1.59 mmol/l and 1.56 mmol/l, p = 0.49) or in triglycerides (1.87 mmol/l and 1.94 mmol/l, p = 0.60). No product-related side effects were reported

CONCLUSION

An interaction was observed between the studied St.-John's-wort-containing product and atorvastatin. Physicians and patients should be aware of this interaction and if treatment with a St. John's wort product is considered necessary, then there may be a need for increasing the dose of atorvastatin.

Pharmacokinetics, safety, and hydrolysis of oral pyrroloquinazolinediamines administered in single and multiple doses in rats

Pyrroloquinazolinediamine (PQD) derivatives such as tetra-acetamide PQD (PQD-A4) and bis-ethylcarbamyl PQD (PQD-BE) were much safer (with therapeutic indices of 80 and 32, respectively) than their parent compound, PQD (therapeutic index, 10). Further evaluation of PQD-A4 and PQD-BE in single and multiple pharmacokinetic (PK) studies as well as corresponding toxicity studies was conducted with rats. PQD-A4 could be converted to two intermediate metabolites (monoacetamide PQD and bisacetamide PQD) first and then to the final metabolite, PQD, while PQD-BE was directly hydrolyzed to PQD without precursor and intermediate metabolites. Maximum tolerant doses showed that PQD-A4 and PQD-BE have only 1/12 and 1/6, respectively, of the toxicity of PQD after a single oral dose. Compared to the area under the concentration-time curve for PQD alone (2,965 ng.h/ml), values measured in animals treated with PQD-A4 and PQD-BE were one-third (1,047 ng.h/ml) and one-half (1,381 ng.h/ml) as high, respectively, after an equimolar dosage, suggesting that PQD was the only agent to induce the toxicity. Similar results were also shown in multiple treatments; PQD-A4 and PQD-BE generated two-fifths and three-fifths, respectively, of PQD concentrations, with 8.8-fold and 3.8-fold safety margins, respectively, over the parent drug. PK data indicated that the bioavailability of oral PQD-A4 was greatly limited at high dose levels, that PQD-A4 was slowly converted to PQD via a sequential three-step process of conversion, and that PQD-A4 was significantly less toxic than the one-step hydrolysis drug, PQD-BE. It was concluded that the slow and smaller release of PQD was the main reason for the reduction in toxicity and that the active intermediate metabolites can still maintain antimalarial potency. Therefore, the candidate with multiple-step hydrolysis of PQD could be developed as a safer potential agent for malaria treatment.

Circulating protein biomarkers of pharmacodynamic activity of sunitinib in patients with metastatic renal cell carcinoma: modulation of VEGF and VEGF-related proteins

BACKGROUND

Sunitinib malate (SUTENT) is an oral, multitargeted tyrosine kinase inhibitor, approved multinationally for the treatment of advanced RCC and of imatinib-resistant or - intolerant GIST. The purpose of this study was to explore potential biomarkers of sunitinib pharmacological activity via serial assessment of plasma levels of four soluble proteins from patients in a phase II study of advanced RCC: VEGF, soluble VEGFR-2 (sVEGFR-2), placenta growth factor (PlGF), and a novel soluble variant of VEGFR-3 (sVEGFR-3).

METHODS

Sunitinib was administered at 50 mg/day on a 4/2 schedule (4 weeks on treatment, 2 weeks off treatment) to 63 patients with metastatic RCC after failure of first-line cytokine therapy. Predose plasma samples were collected on days 1 and 28 of each cycle and analyzed via ELISA.

RESULTS

At the end of cycle 1, VEGF and PlGF levels increased >3-fold (relative to baseline) in 24/54 (44%) and 22/55 (40%) cases, respectively (P < 0.001). sVEGFR-2 levels decreased >or= 30% in 50/55 (91%) cases and >or= 20% in all cases (P < 0.001) during cycle 1, while sVEGFR-3 levels were decreased >or= 30% in 48 of 55 cases (87%), and >or= 20% in all but 2 cases. These levels tended to return to near-baseline after 2 weeks off treatment, indicating that these effects were dependent on drug exposure. Overall, significantly larger changes in VEGF, sVEGFR-2, and sVEGFR-3 levels were observed in patients exhibiting objective tumor response compared with those exhibiting stable disease or disease progression (P < 0.05 for each analyte; analysis not done for PlGF).

CONCLUSION

Sunitinib treatment in advanced RCC patients leads to modulation of plasma levels of circulating proteins involved in VEGF signaling, including soluble forms of two VEGF receptors. This panel of proteins may be of value as biomarkers of the pharmacological and clinical activity of sunitinib in RCC, and of angiogenic processes in cancer and other diseases.

Substituted 6-amino-4H-[1,2]dithiolo[4,3-b]pyrrol-5-ones: Synthesis, structure–activity relationships, and cytotoxic activity on selected human cancer cell lines

An efficient synthesis and the cytotoxic activity of a series of substituted 6-amino-4H-[1,2]dithiolo[4,3-b]pyrrol-5-ones 1a-q is described. The synthesis was accomplished in an expedient manner (seven-steps) from commercially available starting materials. Several of the derivatives tested demonstrated significant in vitro cytotoxic activity against the human cancer cell lines H460 (7nM) and LCC6 (> or =28nM). Following SAR and pharmacokinetic studies a derivative was further evaluated for its in vivo anti-tumor activity against a highly angiogenic human melanoma xenograft where it demonstrated significant efficacy as a mono-therapy and in combination with Taxol and Cisplatin.

Discovery of potent and muscle selective androgen receptor modulators through scaffold modifications

A novel series of imidazolin-2-ones were designed and synthesized as highly potent, orally active and muscle selective androgen receptor modulators (SARMs), with most of the compounds exhibiting low nM in vitro potency in androgen receptor (AR) binding and functional assays. Once daily oral treatment with the lead compound 11a (AR Ki = 0.9 nM, EC50 = 1.8 nM) for 14 days induced muscle growth with an ED50 of 0.09 mg/kg, providing approximately 50-fold selectivity over prostate growth in an orchidectomized rat model. Pharmacokinetic studies in rats demonstrated that the lead compound 11a had oral bioavailability of 65% and a plasma half-life of 5.5 h. On the basis of their preclinical profiles, the SARMs in this series are expected to provide beneficial anabolic effects on muscle with minimal androgenic effects on prostate tissue.

NCX 6560, a nitric oxide-releasing derivative of atorvastatin, inhibits cholesterol biosynthesis and shows anti-inflammatory and anti-thrombotic properties

We compared the lipid-lowering, vasodilating, anti-thrombotic and anti-inflammatory properties of NCX 6560, a novel NO-releasing derivative of atorvastatin, with those of atorvastatin. NCX 6560 and atorvastatin induced similar inhibition of cholesterol biosynthesis in rat smooth muscle cells (IC(50)=1.9+/-0.4 and 3.9+/-1.0 microM, respectively). However, in hyperlipidemic mice, a 5-week oral treatment with NCX 6560 (46.8 mg/kg/day, p.o.) was more effective than equivalent atorvastatin (40 mg/kg/day, p.o.) at lowering serum cholesterol (NCX 6560: -21% vs controls, P<0.05; atorvastatin: -14% vs control, P=NS). In norepinephrine-precontracted rabbit aortic rings, NCX 6560-induced vasodilation (EC(50)=53.5+/-8.3 microM) and in PC12 cells it stimulated cGMP formation (EC(50)=1.8+/-0.7 microM), while atorvastatin was inactive. In lipopolysaccharide from Escherichia coli (LPS)-treated RAW 264.7 macrophages, NCX 6560 reduced iNOS expression and dimer assembly more efficiently than atorvastatin and inhibited nitrite accumulation (IC(50)=6.7+/-1.6 microM) and TNFalpha release. U46619- or collagen plus epinephrine-induced platelet pulmonary thromboembolism in mice was reduced by NCX 6560 at 46.8 mg/kg p.o. (mortality: -44% and -56% vs vehicle, respectively; P<0.05), but not by atorvastatin 40 mg/kg, p.o. In the U46619-induced mortality model, isosorbide mononitrate (ISMN) (20 mg/kg, p.o.), a pure NO-donor, was also active (mortality: -40%, P<0.05). NCX 6560 significantly reduced ex vivo platelet adhesion to collagen at high shear (-31+/-1.3% vs vehicle), and so did ISMN (-33.3+/-1.7% vs vehicle). Atorvastatin was ineffective. NCX 6560, but not atorvastatin, reduced blood pressure in eNOS knockout mice (-16%, P<0.001 vs vehicle), an effect not observed in wild type mice. On the contrary, ISMN provoked a significant drop of blood pressure both in wild type (-20%, P<0.05 vs vehicle) and in eNOS-/- mice (-21%, P<0.05 vs vehicle). In conclusion, NCX 6560 exerts greater lipid-lowering, anti-thrombotic and anti-inflammatory effects than atorvastatin, due to a large extent to NO release.

Therapeutic dose assessment of patient switching from atorvastatin to simvastatin

OBJECTIVE

Patient switching of prescription drug brands within a therapeutic class has become more prevalent with tiered drug plan formularies. Although switching from more expensive brand name drugs to generic equivalents may reduce aggregate prescription costs, therapeutic benefit may be compromised if the patient is not switched to a drug with an equivalent therapeutic profile. This study examined whether patients switching from branded atorvastatin to either a branded or generic simvastatin were prescribed a therapeutically equivalent or higher dose, as opposed to a lower therapeutic dose.

METHODS

Study patients were selected from a national longitudinal database of 1.4 billion annual prescription drug claims. All patients active in the database during the study period (9/01/2005 to 9/30/2006) with a prescription drug claim for atorvastatin in the index month (9/2005) were selected. The 453,409 patients in the study period were followed for 12 months to determine the percent switching to simvastatin and their relative therapeutic doses after switching. Patients switching to the same or lower milligram dose of simvastatin were classified as receiving a lower therapeutic dose compared with their atorvastatin dosing.

RESULTS

Among patients using atorvastatin at the beginning of the study, 13,530 (3%) switched to simvastatin by the end of the study period. Medication changes resulted in a lower therapeutic dose in 38% of the switches. The percent of switches resulting in a lower therapeutic dose were 18% for those switching from 10 mg, 43% for those switching from 20 mg, 73% for those switching from 40 mg, and 100% for those switching from 80 mg.

CONCLUSIONS

A significant proportion of patients switching from atorvastatin to simvastatin received a lower therapeutic dose, which may have an adverse impact on patients' quality of care and health status. Further research is needed to assess the potential negative effect on patient outcomes.

A phase I and pharmacokinetic study of sunitinib administered daily for 2 weeks, followed by a 1-week off period

PURPOSE

Sunitinib, an oral multitargeted tyrosine kinase inhibitor that inhibits VEGFR, PDGFR, FLT3, KIT, and RET, is currently approved for the treatment of imatinib-refractory GIST and advanced renal cell carcinoma at a dose of 50 mg daily for 4 weeks followed by a 2-week off period (4/2 schedule). This trial was performed to investigate the safety, tolerability, and pharmacokinetics of sunitinib 50 mg daily for 2 weeks followed by a 1-week off period (2/1 schedule).

EXPERIMENTAL DESIGN

Twelve patients with advanced refractory malignancies were treated with sunitinib on the 2/1 schedule. Intensive safety monitoring included serial measurements of left ventricular ejection fraction (LVEF). Extensive pharmacokinetic sampling was performed on days 1 and 14 of course 1, and on day 14 of courses 2 and 3 to evaluate sunitinib and the SU12662 metabolite.

RESULTS

Twelve patients received a total of 50 courses with an average (+/-SD) off-drug period of 11.5 +/- 5.7 days. Two patients experienced DLT: one patient had asymptomatic grade 4 elevations in lipase and amylase, and another patient had an asymptomatic grade 2 decline in LVEF in course 1. In total, five patients demonstrated asymptomatic grade 2 declines in LVEF. Other principal effects were similar to previous experience with sunitinib, including fatigue, myelosuppression, skin discoloration, and gastrointestinal effects. Pharmacokinetic studies revealed no significant accumulation of sunitinib or SU12662. One patient with papillary thyroid cancer developed a partial response, and was on study for 16 courses, followed by an additional 18 courses on a continuation protocol.

CONCLUSIONS

The 2/1 schedule of sunitinib 50 mg was tolerable, and no significant drug accumulation was demonstrated. The safety profile on this schedule was consistent with the safety profile of sunitinib when administered on a 4-week on, 2-week off schedule.

Different effects of SLCO1B1 polymorphism on the pharmacokinetics of atorvastatin and rosuvastatin

Thirty-two healthy volunteers with different SLCO1B1 genotypes ingested a 20 mg dose of atorvastatin and 10 mg dose of rosuvastatin with a washout period of 1 week. Subjects with the SLCO1B1 c.521CC genotype (n=4) had a 144% (P<0.001) or 61% (P=0.049) greater mean area under the plasma atorvastatin concentration-time curve from 0 to 48 h (AUC(0-48 h)) than those with the c.521TT (n=16) or c.521TC (n=12) genotype, respectively. The AUC(0-48 h) of 2-hydroxyatorvastatin was 100% greater in subjects with the c.521CC genotype than in those with the c.521TT genotype (P=0.018). Rosuvastatin AUC(0-48 h) and peak plasma concentration (Cmax) were 65% (P=0.002) and 79% (P=0.003) higher in subjects with the c.521CC genotype than in those with the c.521TT genotype. These results indicate that, unexpectedly, SLCO1B1 polymorphism has a larger effect on the AUC of atorvastatin than on the more hydrophilic rosuvastatin.

Atorvastatin glucuronidation is minimally and nonselectively inhibited by the fibrates gemfibrozil, fenofibrate, and fenofibric acid

Gemfibrozil coadministration generally results in plasma statin area under the curve (AUC) increases, ranging from moderate (2- to 3-fold) with simvastatin, lovastatin, and pravastatin to most significant with cerivastatin (5.6-fold). Inhibition of statin glucuronidation has been postulated as a potential mechanism of interaction (Drug Metab Dispos 30:1280-1287, 2002). This study was conducted to determine the in vitro inhibitory potential of fibrates toward atorvastatin glucuronidation. [(3)H]Atorvastatin, atorvastatin, and atorvastatin lactone were incubated with human liver microsomes or human recombinant UDP-glucuronosyltransferases (UGTs) and characterized using liquid chromatography (LC)/tandem mass spectrometry and LC/UV/beta-radioactivity monitor/mass spectrometry. [(3)H]Atorvastatin yields a minor ether glucuronide (G1) and a major acyl glucuronide (G2) with subsequent pH-dependent lactonization of G2 to yield atorvastatin lactone. Atorvastatin lactonization best fit substrate inhibition kinetics (K(m) = 12 microM, V(max) = 74 pmol/min/mg, K(i) = 75 microM). Atorvastatin lactone yields a single ether glucuronide (G3). G3 formation best fit Michaelis-Menten kinetics (K(m) = 2.6 microM, V(max) = 10.6 pmol/min/mg). Six UGT enzymes contribute to atorvastatin glucuronidation with G2 and G3 formation catalyzed by UGTs 1A1, 1A3, 1A4, 1A8, and 2B7, whereas G1 formation was catalyzed by UGTs 1A3, 1A4, and 1A9. Gemfibrozil, fenofibrate, and fenofibric acid inhibited atorvastatin lactonization with IC(50) values of 346, 320, and 291 microM, respectively. Based on unbound fibrate concentrations at the inlet to the liver, these data predict a small increase in atorvastatin AUC (approximately 1.2-fold) after gemfibrozil coadministration and no interaction with fenofibrate. This result is consistent with recent clinical reports indicating minimal atorvastatin AUC increases ( approximately 1.2- to 1.4-fold) with gemfibrozil.

Sunitinib: a VEGF and PDGF receptor protein kinase and angiogenesis inhibitor

Sunitinib (SU-11248, Sutent) inhibits at least eight receptor protein-tyrosine kinases including vascular endothelial growth factor receptors 1-3 (VEGFR1-VEGFR3), platelet-derived growth factor receptors (PDGFRalpha and PDGFRbeta), stem cell factor receptor (Kit), Flt-3, and colony-stimulating factor-1 receptor (CSF-1R). VEGFR1 and VEGFR2 play key roles in vasculogenesis and angiogenesis. PDGFRbeta, which is found in pericytes that surround capillary endothelial cells, plays a pivotal role in stabilizing the vascular endothelium. Sunitinib inhibits angiogenesis by diminishing signaling through VEGFR1, VEGFR2, and PDGFRbeta. Renal cell cancers that have metastasized, or spread from the primary tumor, exhibit extensive vascularity, and sunitinib is approved for the treatment of these neoplasms. Activating Kit mutations occur in about 85% of gastrointestinal stromal tumors and activating PDGFRalpha mutations occur in about 5% of these tumors. Sunitinib is approved for the treatment of those tumors that are resistant to imatinib (STI-571, Gleevec), another Kit and PDGFRalpha protein-tyrosine kinase inhibitor. Both sunitinib and imatinib bind reversibly to the ATP binding site of their target kinases and thereby inhibit their catalytic activity.