The expectation is that if an agent is good for one form of a specific form of a spondyloarthritis like psoriatic arthritis, it must be good for all of them. Unfortunately, that is not always the case. Sometimes the benefits of a specific therapy are limited to a specific form of the illness. That is the case with apremilast or Otezla which has been shown to be effective in psoriatic arthritis.

A phase-3 placebo-controlled study was conducted over a 6 year period to study the benefit of apremilast 20 mg twice a day, versus 30 mg twice a day, and placebo in ankylosing spondylitis (AS) patients. The official endpoint of the study was 20% improvement at week 16. Also studied were the effects of the drug on radiographic changes after 104 weeks.

A total of 490 participants with active AS (163 apremilast 30 mg twice a day, 163 apremilast 20 mg twice a day, and 164 placebo) completed the study. At 16 weeks. About one third of all groups had a 20% improvement. No significant differences in radiographic changes were noted among the study groups. More adverse reactions including diarrhea, nausea, and headaches were noted with apremilast.

The authors suggest that the lack of response of apremilast in AS patients relates to the inhibitory effect of apremilast (a phosphodiesterase 4 inhibitor) on interleukin (IL)-23 which is not an important factor in the development and progression of AS.

References:

1. Taylor PC. Et al. a phase III randomized study of apremilast, an oral phosphodiesterase 4 inhibitor, for active ankylosing spondylitis. J Rheumatol 2021 Feb 15;jrheum.201088.doi: 10.3899/jrheum 201088