Michael Kaufman

Structures of human MAP kinase kinase 1 (MEK1) and MEK2 describe novel noncompetitive kinase inhibition.

MEK1 and MEK2 are closely related, dual-specificity tyrosine/threonine protein kinases found in the Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) signaling pathway. Approximately 30% of all human cancers have a constitutively activated MAPK pathway, and constitutive activation of MEK1 results in cellular transformation. Here we present the X-ray structures of human MEK1 and MEK2, each determined as a ternary complex with MgATP and an inhibitor to a resolution of 2.4 Å and 3.2 Å, respectively. The structures reveal that MEK1 and MEK2 each have a unique inhibitor-binding pocket adjacent to the MgATP-binding site. The presence of the potent inhibitor induces several conformational changes in the unphosphorylated MEK1 and MEK2 enzymes that lock them into a closed but catalytically inactive species. Thus, the structures reported here reveal a novel, noncompetitive mechanism for protein kinase inhibition.

Daclizumab in active relapsing multiple sclerosis (CHOICE study): a phase 2, randomised, double-blind, placebo-controlled, add-on trial with interferon beta

BACKGROUND Daclizumab, a humanised monoclonal antibody, reduced multiple sclerosis disease activity in previous non-randomised studies. We aimed to assess whether daclizumab reduces disease activity in patients with active relapsing multiple sclerosis who are receiving interferon beta treatment. METHODS We did a phase 2, randomised, double-blind, placebo-controlled study at 51 centres in the USA, Canada, Germany, Italy, and Spain. Patients with active relapsing multiple sclerosis who were taking interferon beta were randomly assigned to receive add-on subcutaneous daclizumab 2 mg/kg every 2 weeks (interferon beta and high-dose daclizumab group), daclizumab 1 mg/kg every 4 weeks (interferon beta and low-dose daclizumab group), or interferon beta and placebo for 24 weeks. The randomisation scheme was generated by Facet Biotech. All patients and assessors were masked to treatment with the exception of Facet Biotech bioanalysts who prepared data for the data safety monitoring board or generated pharmacokinetic or pharmacodynamic data, a drug accountability auditor, and the site pharmacist. The primary endpoint was total number of new or enlarged gadolinium contrast-enhancing lesions measured on brain MRI scans every 4 weeks between weeks 8 and 24. Effects of daclizumab on prespecified subsets of lymphocytes and quantitative T-cell proliferative response were assessed in an exploratory pharmacodynamic substudy. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00109161. FINDINGS From May, 2005, to March, 2006, 288 patients were assessed for eligibility, and 230 were randomly assigned to receive interferon beta and high-dose daclizumab (n=75), interferon beta and low-dose daclizumab (n=78), or interferon beta and placebo (n=77). The adjusted mean number of new or enlarged gadolinium contrast-enhancing lesions was 4.75 in the interferon beta and placebo group compared with 1.32 in the interferon beta and high-dose daclizumab group (difference 72%, 95% CI 34% to 88%; p=0.004) and 3.58 in the interferon beta and low-dose daclizumab group (25%, -76% to 68%; p=0.51). In the pharmacodynamic substudy, daclizumab was not associated with significant changes in absolute numbers of T cells, B cells, or natural killer cells, or T-cell proliferative response compared with interferon beta alone. The number of CD56(bright) natural killer cells was seven to eight times higher in both daclizumab groups than in the interferon beta and placebo group (interferon beta and low-dose daclizumab group p=0.002; interferon beta and high-dose daclizumab group p<0.0001). Common adverse events were equally distributed across groups. INTERPRETATION Add-on daclizumab treatment reduced the number of new or enlarged gadolinium contrast-enhancing lesions compared with interferon beta alone and might reduce multiple sclerosis disease activity to a greater extent than interferon beta alone. FUNDING Facet Biotech and Biogen Idec.

The discovery of the benzhydroxamate MEK inhibitors CI-1040 and PD 0325901

A novel series of benzhydroxamate esters derived from their precursor anthranilic acids have been prepared and have been identified as potent MEK inhibitors. 2-(2-Chloro-4-iodo-phenylamino)-N-cyclopropylmethoxy-3,4-difluoro-benzamide, CI-1040, was the first MEK inhibitor to demonstrate in vivo activity in preclinical animal models and subsequently became the first MEK inhibitor to enter clinical trial. CI-1040 suffered however from poor exposure due to its poor solubility and rapid clearance, and as a result, development of the compound was terminated. Optimization of the diphenylamine core and modification of the hydroxamate side chain for cell potency, solubility, and exposure with oral delivery resulted in the discovery of the clinical candidate N-(2,3-dihydroxy-propoxy)-3,4-difluoro-2-(2-fluoro-4-iodo-phenylamino)-benzamide PD 0325901.

The significant change for the Timed 25-foot Walk in the multiple sclerosis functional composite.

The Timed 25-Foot Walk is under evaluation as a clinical tool to follow patients with MS. Several approaches have been taken to define a clinically significant change in this measurement. This study was undertaken to define the range of values expected for the Timed 25-Foot Walk and to correlate prospectively the change in walk-time that occurs during an exacerbation of MS associated with subjective difficulty walking. Five results from this study are emphasized. (1) Patients who were minimally affected by MS frequently walked 25 feet between three and five seconds. (2) the walk-time variability, defined as the ratio of the longest to the shortest walk-time, minus 1, times 100%, for three consecutive trials was generally 20% or less; (3) if the two fastest walk-times obtained in three trials were compared, the walk-time variability was almost always 10% or less; (4) for clinically stable individuals, the walk-times of single trials separated by 12 months or less generally varied less than 20%; and (5) patients who complained of difficulty walking, but who did not have changes otherwise detectable by examination, generally had a prolongation of walk-time. These results suggest that an increase of more than 20% in the Timed 25-Foot Walk may indicate a significant change in gait.

MS disease activity in RESTORE A randomized 24-week natalizumab treatment interruption study

Objective: RESTORE was a randomized, partially placebo-controlled exploratory study evaluating multiple sclerosis (MS) disease activity during a 24-week interruption of natalizumab. Methods: Eligible patients were relapse-free through the prior year on natalizumab and had no gadolinium-enhancing lesions on screening brain MRI. Patients were randomized 1:1:2 to continue natalizumab, to switch to placebo, or to receive alternative immunomodulatory therapy (other therapies: IM interferon β-1a [IM IFN-β-1a], glatiramer acetate [GA], or methylprednisolone [MP]). During the 24-week randomized treatment period, patients underwent clinical and MRI assessments every 4 weeks. Results: Patients (n = 175) were randomized to natalizumab (n = 45), placebo (n = 42), or other therapies (n = 88: IM IFN-β-1a, n = 17; GA, n = 17; MP, n = 54). Of 167 patients evaluable for efficacy, 49 (29%) had MRI disease activity recurrence: 0/45 (0%) natalizumab, 19/41 (46%) placebo, 1/14 (7%) IM IFN-β-1a, 8/15 (53%) GA, and 21/52 (40%) MP. Relapse occurred in 4% of natalizumab patients and in 15%–29% of patients in the other treatment arms. MRI disease activity recurred starting at 12 weeks (n = 3 at week 12) while relapses were reported as early as 4–8 weeks (n = 2 in weeks 4–8) after the last natalizumab dose. Overall, 50/167 patients (30%), all in placebo or other-therapies groups, restarted natalizumab early because of disease activity. Conclusions: MRI and clinical disease activity recurred in some patients during natalizumab interruption, despite use of other therapies. Classification of evidence: This study provides Class II evidence that for patients with MS taking natalizumab who are relapse-free for 1 year, stopping natalizumab increases the risk of MS relapse or MRI disease activity as compared with continuing natalizumab.

Inhibition of RAF Isoforms and Active Dimers by LY3009120 Leads to Anti-tumor Activities in RAS or BRAF Mutant Cancers

LY3009120 is a pan-RAF and RAF dimer inhibitor that inhibits all RAF isoforms and occupies both protomers in RAF dimers. Biochemical and cellular analyses revealed that LY3009120 inhibits ARAF, BRAF, and CRAF isoforms with similar affinity, while vemurafenib or dabrafenib have little or modest CRAF activity compared to their BRAF activities. LY3009120 induces BRAF-CRAF dimerization but inhibits the phosphorylation of downstream MEK and ERK, suggesting that it effectively inhibits the kinase activity of BRAF-CRAF heterodimers. Further analyses demonstrated that LY3009120 also inhibits various forms of RAF dimers including BRAF or CRAF homodimers. Due to these unique properties, LY3009120 demonstrates minimal paradoxical activation, inhibits MEK1/2 phosphorylation, and exhibits anti-tumor activities across multiple models carrying KRAS, NRAS, or BRAF mutation.

Update on Best Practice Recommendations for Anesthetic Perioperative Care and Pain Management in Weight Loss Surgery, 2004–2007

To reevaluate and update evidence‐based best practice recommendations published in 2004 for anesthetic perioperative care and pain management in weight loss surgery (WLS), we performed a systematic search of English‐language literature on anesthetic perioperative care and pain management in WLS published between April 2004 and May 2007 in MEDLINE and the Cochrane Library. We identified relevant abstracts by using key words, retrieved full text articles, and stratified the resulting evidence according to systems used in established evidence‐based models. We updated prior evidence‐based best practice recommendations based upon interim literature. In instances of controversial or inadequate scientific evidence, the task force reached consensus recommendations following evaluation of the best available information and expert opinion. The search yielded 1,788 abstracts, with 162 potentially relevant titles; 45 were reviewed in detail. Despite more information on perioperative management of patients with obstructive sleep apnea (OSA), evidence to support preoperative testing and treatment or to guide perioperative monitoring is scarce. New evidence on appropriate intraoperative dosing of muscle relaxants allows for greater precision in their use during WLS. A novel application of α−2 agonists for perioperative anesthetic care is emerging. Key elements that may enhance patient safety include integration of the latest evidence on WLS, obesity, and collaborative multidisciplinary care into clinical care. However, large gaps remain in the evidence base.

Multiple sclerosis: severity and progression rate in African Americans compared with whites.

Kaufman MD, Johnson SK, Moyer D, Bivens J, Norton HJ: Multiple sclerosis: Severity and progression rate in African Americans compared with whites. Am J Phys Med Rehabil 2003;82:582–590. ObjectiveAlthough epidemiology indicates that multiple sclerosis is more common among whites than African Americans, the course of disease may be more aggressive among African Americans. This study examines disease course in a large multiple sclerosis clinic population. DesignA case-controlled, retrospective record review compared the severity of multiple sclerosis for African Americans and for whites. Because the baseline demographics of the two groups differed, we performed analyses of multiple subgroups in an attempt to control for various characteristics. ResultsConsistent evidence of more disability in African Americans compared with whites was found, although subgroups were often too small to establish statistical significance. African Americans had a higher mean Expanded Disability Status Scale score than whites in a subgroup selected to minimize differences in access to care and disease perceptions. African Americans reported limb weakness as a presenting symptom of multiple sclerosis more frequently than did whites. When patients were followed at our multiple sclerosis center, rates of disease progression were nearly identical. ConclusionsMore African Americans than whites experience pyramidal system involvement early in multiple sclerosis, leading to greater disability as measured by the ambulation-sensitive Expanded Disability Status Scale. Once patients have moderate difficulty walking, the rate of progression is the same for both groups, albeit occurring at a later age for whites than for African Americans.

The PROMiSe trial: baseline data review and progress report

The PRO MiSe trial is a multinational, multicentre, double-blind, placebo -controlled trial evaluating the effects of glatiramer acetate treatment over 3 years in patients with primary progressive multiple sclerosis (PPMS). A total of 943 patients were enrolled, and all those remaining on-study had completed at least 24 months as of O ctober 2002. Baseline clinical and MRI character istics and select correlations are reported here. A total of 3.9% of patients exhibited confirmed relapse over 1904 patient-years of exposure, indicating success of efforts to exclude relapsing MS types. O f the 26.3% of patients who have prematurely withdrawn from the study, only 36% discontinued after meeting the study primary endpoint of disease progression. The progression rate in patients in the low Expanded Disability Status Scale (EDSS) stratum (3.0-5.0) observed thus far is markedly lower than the 50% annual progression rate estimate used for determining size and statistical power of the trial; progression was observed in 16.1% of patients with 12 months of study exposure. These early findings raise some concern about the ability of the trial to demonstrate a significant treatment effect, and suggest that the short-term natural history of PPMS may not be as aggressive as previously assumed.

2-Alkylamino- and alkoxy-substituted 2-amino-1,3,4-oxadiazoles-O-Alkyl benzohydroxamate esters replacements retain the desired inhibition and selectivity against MEK (MAP ERK kinase).

This paper reports a second generation MEK inhibitor. The previously reported potent and efficacious MEK inhibitor, PD-184352 (CI-1040), contains an integral hydroxamate moiety. This compound suffered from less than ideal solubility and metabolic stability. An oxadiazole moiety behaves as a bioisostere for the hydroxamate group, leading to a more metabolically stable and efficacious MEK inhibitor.