I've been looking to see what new medications might be in clinical trials for PsA. You can find the clinical trials at http://clinicaltrials.gov/ct2/results?term=psoriatic+arthritis ... or try other search terms. Then if you look for completed studies, if you google around enough, you can maybe find the results of the trial. I did a little work so on one medicine, secukinumab (AIN 457). The suffix "mab" means its an anti-body, But this an TNF-Alpha antibody. It goes after interleukin which means it may be effective where the TNF fighters aren't. Also it might have very different side effects.
I still haven't figured out exactly what ACR20, ACR50 and ARC70 mean except that even ACR20 is better than nothing (I think) and higher is better. 89% of participants on the receiving secukinumab for 16 weeks at ACR20 or better compared to 46% for placebo. most participants were already on MTX. ACR 50 had 27% versus 15% for placebo and ACR70 had 8% versus 0% for placebo.
The Euler response rate which is maybe more intuitive had for the drug: no response 31%, Moderate response 31%, Good response 31%. The placebo was 62%, 19% and 19% respectively.
The data from that study is at: http://knol.google.com/k/kyle-tang/ain457-secukinumab/2tte8pje5bjpa/1#
There's another article at http://www.reuters.com/article/2010/10/06/novartis-secukinumab-idUSLDE6950KA20101006
I think secukinumab shows great promise mainly because it's a totally different medicine from Enbrel, Humira and Remicade. There are more trials open now.
There are several other medications listed in the trials and I don't have time to hunt them all down. Maybe others can also contribute to this thread.