Metabolism-blocked antifolates as potential anti-rheumatoid arthritis agents: 4-Amino-4-deoxy-5,8,10-trideazapteroyl-d,l-4′-methyleneglutamic acid (CH-1504) and its analogs

High red blood cell folate is associated with an increased risk of death among adults with diabetes, a 15-year follow-up of a national cohort

BACKGROUND AND AIM

To describe the mortality and fatality of diabetes and assess their relationship with the level of red blood cell (RBC) folate.

METHODS AND RESULT

We analyzed the data of 526 adults with diabetes who participated in the National Health and Nutrition Examination Survey (1991-1994) as the baseline examination, and were followed up through December 31, 2006. Estimates of the hazard ratios (HRs) of selected death causes for individuals with different levels of RBC folate were obtained from Cox proportional hazards regression. A total of 295 deaths were recorded by the end of a 15-year follow-up with a mortality rate of 58.48 per 1000 person year (py). Diabetes was listed as a contributing cause for 136 deaths, accounting for 46.1% of the total deaths with a fatality rate 26.96 per 1000 py. Mortality rate for all-cause in the group with upper quartile of RBC folate was almost twice as high as that among the group with lower quartile, 82.75 vs. 44.10 per 1000 py. After adjusting for covariates, including serum concentration of vitamin B12, cotinine, homocysteine and the history of cardio-cerebral vascular diseases assessed at the baseline, the HRs for dying from any causes were 1.00 (reference), 1.82 (95% CI = 1.25-2.66) and 2.10 (1.37-3.20) among diabetic adults with lower, intermediate, and upper quartiles of RBC folate.

CONCLUSION

Diabetes was listed as a contributing cause for less than half of the deaths among adults with diabetes after 15+ years of follow-up; high RBC folate concentration was associated with an elevated risk of death among adults with diabetes.

Antifolate agents: a patent review (2010 - 2013)

INTRODUCTION

The folate biosynthetic pathway, responsible for the de novo synthesis of thymidine and other key cellular components, is essential in all life forms and is especially critical in rapidly proliferating cells. As such, druggable targets along this pathway offer opportunities to impact many disease states such as cancer, infectious disease and autoimmune disease. In this article, recent progress on the development of antifolate compounds is reviewed.

AREAS COVERED

The evaluation of the patent literature during the period 2010 - 2013 focused on any compounds inhibiting recognized targets on the folate biosynthetic pathway.

EXPERT OPINION

The folate pathway constitutes a well-validated and well-characterized set of targets; this pathway continues to elicit considerable enthusiasm for new drug discovery from both academic and industrial pharmaceutical research groups. Within the pathway, the enzymes dihydrofolate reductase and thymidylate synthase persist as the most attractive targets for new drug discovery for the treatment of cancer and infectious disease. Importantly, new potential targets for antifolates such as those on the purine biosynthetic pathway have been recently explored. The use of structure-based drug design is a major aspect in modern approaches to these drug targets.

Efficacy and Safety of CH-1504, a Metabolically Stable Antifolate, in Patients with Active Rheumatoid Arthritis: Results of a Phase II Multicenter Randomized Study

Objective.

To investigate the potential efficacy, safety, and tolerability of daily use of CH-1504 in patients with active rheumatoid arthritis (RA). US National Institutes of Health database no. NCT00658047.

Methods.

In our phase II randomized double-blind double-dummy study, patients naive to methotrexate (MTX; n = 201) and having moderate to severe RA received either CH-1504 (0.25 mg, 0.5 mg, or 1.0 mg once-daily oral doses) or MTX (titrated to 20.0 mg once-weekly oral doses). All received weekly 10-mg folate supplementation. Efficacy and safety were assessed at 2, 4, 8, and 12 weeks, with a treatment-free followup at 16 weeks. Safety and tolerability were assessed. Primary efficacy endpoint was proportion of patients achieving ACR20 response at Week 12. Secondary endpoints included difference from baseline in the 28-joint Disease Activity Score (DAS28) and individual components of the American College of Rheumatology (ACR) composite index.

Results.

Demographic characteristics were similar in all treatment groups: mean age 54.3 ± 11.4 years, female sex 87%, mean baseline DAS28 6.6 ± 0.9. At Week 12, CH-1504 demonstrated comparable efficacy compared to MTX as measured by ACR20, DAS28, and ACR composite core-set measures, including tender and swollen joints. No dose-response relationship was observed. Adverse events across treatment groups were mild. Liver enzyme levels increased from baseline to Week 16 in the MTX group, with qualitatively lesser increases in the CH-1504 groups. Two patients in the MTX group withdrew because of gastrointestinal-related adverse events. CH-1504 appeared safe and well tolerated at all dose levels.

Conclusion.

CH-1504 has comparable efficacy to MTX and is safe and well tolerated. Metabolically stable antifolates are a promising therapeutic option that warrants further study.

[The future of methotrexate therapy and other folate inhibitors]

Because of its good effectiveness and tolerability, methotrexate (MTX) has been the most important DMARD for the treatment of rheumatoid arthritis (RA) worldwide for many years. Thus the treatment of this disease is strongly based on the principle of folate inhibition. Recent years have brought new insights into the pharmacology and mechanisms of action of MTX. As a result, it now appears possible to further develop folate inhibitors to increase effectiveness and specificity. Polyglutamation of the drug, a metabolic step which appears to play a role both in terms of therapeutic effects and hepatic side effects, might be a possible starting point. Moreover, methods of targeted drug delivery intended to increase drug accumulation at the site of inflammation can increase the effectiveness of treatment and reduce toxicity. Albumin-coupled and liposomally-conjugated MTX, both of which inhibit inflammation in animal models more potently than MTX, are undergoing preclinical evaluation. It was recognized that activated synovial macrophages upregulate folate receptor ß (FR-ß) expression and that MTX can become active by this pathway. This finding makes it possible to develop new FR-ß-specific folate inhibitors with specificity for this pathophysiologically important cell population.