Variability symptoms and conditions

Results: DNA was collected from 252 participants: 69% were white, 26% were African American. Twenty-eight SNPs in the ALOX5, LTA4H, LTC4S, MRP1, and cysLT1R genes, and an ALOX5 repeat polymorphism were successfully typed. There were racial disparities in allele frequencies in 17 SNPs and in the repeat polymorphism. Association analyses were performed in 61 whites. Associations were found between genotypes of SNPs in the ALOX5 (rs2115819) and MRP1 (rs119774) genes and changes in FEV1 (p < 0.05), and between two SNPs in LTC4S (rs730012) and in LTA4H (rs2660845) genes for exacerbation rates. Mutant ALOX5 repeat polymorphism was associated with decreased exacerbation rates. There was strong linkage disequilibrium between ALOX5 SNPs. Associations between ALOX5 haplotypes and risk of exacerbations were found.

Conclusions: Genetic variation in leukotriene pathway candidate genes contributes to variability in montelukast response.

http://ajrccm.atsjournals.org/cgi/content/full/173/4/379

Some of you who are following this site may remember that I posted that when I was following the pathways of the leukeotriene receptor antagonist Singulair that I got to a point where I concluded that there has to be a genetic component (meaning that there are different gene groups of people) and that the efficacy of Singulair (and possibly safety) can vary depending upon what gene group people are in. So I took a little time to see if anybody else was already studying that issue. And YES, they are -- including Merck.

quote:

" However, logically one might predict that it will be the combination of the polymorphisms in these different key regulatory enzymes and receptors that may ultimately determine treatment response. There have been some attempts to tease out the possible contribution of different genes important in this pathway for treatment response to a Cys leukotriene receptor 1 antagonist.18 However, because of the number of potential gene variants that may contribute to efficacy, large studies will be needed to fully evaluate the potential contribution of pharmacogenetic variability in this pathway to treatment response to Cys leukotriene receptor 1 antagonists. Work in the cardiovascular field has demonstrated the potential importance of genetic variants in this pathway to disease risk and also to treatment response,19 suggesting the potential for important effects to be defined in asthma."

(Chest. 2006;130:1873-1878.)
© 2006 American College of Chest Physicians

Pharmacogenetics of Asthma
Ian P. Hall, DM
* From the Division of Therapeutics and Molecular Medicine, University Hospital of Nottingham, Nottingham, UK.
Correspondence to: Ian P. Hall, DM, Division of Therapeutics and Molecular Medicine, University Hospital of Nottingham, Nottingham NG7 2UH, UK; e-mail: Ian.Hall@nottingham.ac.uk

http://www.chestjournal.org/cgi/content/full/130/6/1873

And Merck sponsored a study on this which is now completed.

http://clinicaltrials.gov/ct2/show/NCT00116324?intr=%22Montelukast%22&rank=79

Of course, it was sponsored by Merck and paid for by Merck.

I don't know if the study discovered anything but I believe this is an indication that Merck acknowledges genetic differences in populations that may predict the success of montelukast.

I am not any where close to being an expert in this field. I have another background but I believe that there are experts who can tell you exactly why you had side effects from Singulair.