in approximately 25% of patients. these flares tend to occur within one week after starting regular use of the nsaid. in contrast, acetaminophen (paracetamol) and aspirin appear to be safe. celecoxib (celebrex), a cox-2 inhibitor, also appears to be safe, at least in short-term studies of patients in remission and on medication for their crohn's disease. research egg of trichuris spp. whipworm. trichuris suis or pig whipworm has been investigated for treatment of crohn's disease. many clinical trials have been recently completed or are ongoing for new therapies for crohn's disease. they include the following: certolizumab is a pegylated fab fragment of a humanized anti-tnfα monoclonal antibody that was found to have efficacy over placebo in one large trial. traficet-en/ccx282/gsk'786/vercirnon is a ccr9 chemokine receptor antagonist intended to modulate immune response. it failed in phase iii clinical trials, showing no improvement over a placebo. abt-874 is a human anti-il-12 monoclonal antibody being developed by abbott laboratories in conjunction with cambridge antibody technology for the treatment of multiple autoimmune diseases, including crohn's disease. phase ii trials showed promising results, sargramostim, or granulocyte-monocyte colony stimulating factor (gm-csf), has been shown to substantially improve health-related quality of life in pilot studies, measured by an increase in score on a 32-item ibd questionnaire. a recent phase ii trial showed that sargramostim significantly decreased cd severity (48%, compared with 26% in the placebo group) and improved quality of life (40%, versus 19% for placebo). trichuris suis is a pig whipworm that been shown in one study to improve crohn's disease symptoms. autologous stem cell transplants have also been evaluated. rifabutin, clarithromycin and clofazimine are antibiotics designed to attack mycobacterium avium subsp. paratuberculosis, which may be a cause of crohn's disease. this treatment, called myoconda, is being tested by giaconda. a pilot study found that low-dose naltrexone, a very inexpensive drug, helped patients with active crohn's disease. in the study, 89% of patients exhibited a response to therapy, and 67% achieved remission within four weeks.