Inhibition of the C1s Protease and the Classical Complement Pathway by 6-(4-Phenylpiperazin-1-yl)Pyridine-3-Carboximidamide and Chemical Analogs

The classical pathway (CP) is a potent mechanism for initiating complement activity and is a driver of pathology in many complement-mediated diseases. The CP is initiated via activation of complement component C1, which consists of the pattern recognition molecule C1q bound to a tetrameric assembly of proteases C1r and C1s. Enzymatically active C1s provides the catalytic basis for cleavage of the downstream CP components, C4 and C2, and is therefore an attractive target for therapeutic intervention in CP-driven diseases. Although an anti-C1s mAb has been Food and Drug Administration approved, identifying small-molecule C1s inhibitors remains a priority. In this study, we describe 6-(4-phenylpiperazin-1-yl)pyridine-3-carboximidamide (A1) as a selective, competitive inhibitor of C1s. A1 was identified through a virtual screen for small molecules that interact with the C1s substrate recognition site. Subsequent functional studies revealed that A1 dose-dependently inhibits CP activation by heparin-induced immune complexes, CP-driven lysis of Ab-sensitized sheep erythrocytes, CP activation in a pathway-specific ELISA, and cleavage of C2 by C1s. Biochemical experiments demonstrated that A1 binds directly to C1s with a Kd of ∼9.8 μM and competitively inhibits its activity with an inhibition constant (Ki) of ∼5.8 μM. A 1.8-Å-resolution crystal structure revealed the physical basis for C1s inhibition by A1 and provided information on the structure-activity relationship of the A1 scaffold, which was supported by evaluating a panel of A1 analogs. Taken together, our work identifies A1 as a new class of small-molecule C1s inhibitor and lays the foundation for development of increasingly potent and selective A1 analogs for both research and therapeutic purposes.

European LeukemiaNet-defined primary refractory acute myeloid leukemia: the value of allogeneic hematopoietic stem cell transplant and overall response

We sought to appraise the value of overall response and salvage chemotherapy, inclusive of allogeneic hematopoietic stem cell transplant (AHSCT), in primary refractory acute myeloid leukemia (prAML). For establishing consistency in clinical practice, the 2017 European LeukemiaNet (ELN) defines prAML as failure to attain CR after at least 2 courses of intensive induction chemotherapy. Among 60 consecutive patients (median age 63 years) correspondent with ELN-criteria for prAML, salvage was documented in 48 cases, 30/48 (63%) being administered intensive chemotherapy regimens and 2/48 consolidated with AHSCT as first line salvage. 13/48 (27%) attained response: CR, 7/13 (54%), CRi, 2/13 (15%), MLFS, 4/13 (31%). The CR/CRi rate was 9/48 (19%), with CR rate of 7/48 (15%). On univariate analysis, intermediate-risk karyotype was the only predictor of response (44% vs 17% in unfavorable karyotype; P = 0.04). Administration of any higher-dose (>1 g/m²) cytarabine intensive induction (P = 0.50), intensive salvage chemotherapy (P = 0.72), targeted salvage (FLT3 or IDH inhibitors) (P = 0.42), greater than 1 salvage regimen (P = 0.89), age < 60 years (P = 0.30), and de novo AML (P = 0.10) did not enhance response achievement, nor a survival advantage. AHSCT was performed in 12 patients with (n = 8) or without (n = 4) CR/CRi/MLFS. 1/2/5-year overall survival (OS) rates were 63%/38%/33% in patients who received AHSCT (n = 12) vs 27%/0%/0% in those who achieved CR/CRi/MLFS but were not transplanted (n = 5), vs 14%/0%/0% who were neither transplanted nor achieved CR/CRi/MLFS (n = 43; P < 0.001); the median OS was 18.6, 12.6 and 5.6 months, respectively. Although CR/CRi/MLFS bridged to AHSCT (n = 8), appeared to manifest a longer median OS (20 months), vs (13.4 months) for those with no response consolidated with AHSCT (n = 4), the difference was not significant P = 0.47. We conclude AHSCT as indispensable for securing long-term survival in prAML (p = 0.03 on multivariate analysis), irrespective of response achievement.

Increasing skeletal muscle fatty acid transport protein 1 (FATP1) targets fatty acids to oxidation and does not predispose mice to diet-induced insulin resistance

AIMS/HYPOTHESIS

We examined in skeletal muscle (1) whether fatty acid transport protein (FATP) 1 channels long-chain fatty acid (LCFA) to specific metabolic fates in rats; and (2) whether FATP1-mediated increases in LCFA uptake exacerbate the development of diet-induced insulin resistance in mice. We also examined whether FATP1 is altered in insulin-resistant obese Zucker rats.

METHODS

LCFA uptake, oxidation and triacylglycerol esterification rates were measured in control and Fatp1-transfected soleus muscles to determine FATP1-mediated lipid handling. The effects of FATP1 on insulin sensitivity and triacylglycerol accumulation were determined in high-fat diet-fed wild-type mice and in muscle-specific Fatp1 (also known as Slc27a1) overexpressing transgenic mice driven by the muscle creatine kinase (Mck [also known as Ckm]) promoter. We also examined the relationship between FATP1 and both fatty acid transport and metabolism in insulin-resistant obese Zucker rats.

RESULTS

Transient Fatp1 overexpression in soleus muscle increased (p < 0.05) palmitate transport (24%) and oxidation (35%), without altering triacylglycerol esterification or the intrinsic rate of palmitate oxidation in isolated mitochondria. In Mck/Fatp1 animals, Fatp1 mRNA and 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid uptake in skeletal muscle were upregulated (75%). However, insulin sensitivity and intramuscular triacylglycerol content did not differ between wild-type and Mck/Fatp1 mice following a 16 week high-fat diet. In insulin-resistant obese Zucker rats, LCFA transport and triacylglycerol accumulation were increased (85% and 24%, respectively), but this was not attributable to Fatp1 expression, as neither total cellular nor sarcolemmal FATP1 content were altered.

CONCLUSIONS/INTERPRETATION

Overexpression of Fatp1 in skeletal muscle increased the rate of LCFA transport and channelled these lipids to oxidation, not to intramuscular lipid accumulation. Therefore, skeletal muscle FATP1 overabundance does not predispose animals to diet-induced insulin resistance.

Cessation of medication for people with schizophrenia already stable on chlorpromazine

BACKGROUND

Chlorpromazine, one of the first generation of antipsychotic drugs, is effective in the treatment of schizophrenia. For most people schizophrenia is a life-long disorder but about a quarter of those who have a first psychotic breakdown do not go on to experience further breakdowns. Most people with schizophrenia are prescribed antipsychotic drugs, although use is often intermittent. The effects of stopping medication are not well researched in the context of systematic reviews.

OBJECTIVES

To quantify the effects of stopping chlorpromazine for people with schizophrenia stable on this drug.

SEARCH STRATEGY

We supplemented an electronic search of the Cochrane Schizophrenia Group Trials Register (March 2006) with reference searching of all identified studies.

SELECTION CRITERIA

We included all relevant randomised clinical trials.

DATA COLLECTION AND ANALYSIS

We independently inspected citations and abstracts, ordered papers and re-inspected and quality assessed these. We independently extracted data and resolved disputes during regular meetings. We analysed dichotomous data using fixed effects relative risk (RR) and the 95% confidence interval (CI). For continuous data, where possible, we calculated the weighted mean difference (WMD). We excluded the data where more than 40% of people were lost to follow up.

MAIN RESULTS

We included ten trials involving 1042 people with schizophrenia stable on chlorpromazine. Even in the short term, those who remained on chlorpromazine were less likely to experience a relapse compared to people who stopped taking chlorpromazine (n=376, 3 RCTs, RR 6.76 CI 3.37 to 13.54, NNH XX CI XX to XX). Medium term (n=850, 6 RCTs, RR 4.04 CI 2.81 to 5.8, NNH 4 CI 3 to 7) and long term data were similar (n=510, 3 RCTs, RR 1.70 CI 1.44 to 2.01, NNH XX CI XX to XX). People allocated to chlorpromazine withdrawal were not significantly more likely to stay in the study compared with those continuing chlorpromazine treatment (n=374, 1 RCT, RR 1.14 CI 0.55 to 2.35). In sensitivity analyses, there was a significant difference in the 'relapse' outcome between trials for those diagnosed according to checklist criteria compared to those with a clinical diagnosis.

AUTHORS' CONCLUSIONS

This review confirms clinical experience and quantifies the risks of stopping chlorpromazine medication for a group of people with schizophrenia who are stable on this drug. With its moderate adverse effects, chlorpromazine is likely to remain one of the most widely prescribed treatments for schizophrenia.