ICYMI: JAKi in inflammatory myositis? Save

The ACR Convergence meeting in Washington (#ACR24) will showcase nearly 3000 abstracts. With the expanding use of JAK inhibitors, there will be some interesting presentations for off label use.  There have been some uncontrolled data that tofacitinib reduced inflammatory myositis disease activity and improved calcinosis in patients with refractory myositis (1).

Abstract 1731 is a small RCT of baricitinib in inflammatory myositis comparing early start baricitinib to later start (2). This methodology is similar to the RIM (Rituximab in Myositis trial where rituximab was compared to rituximab with a delayed start) (3). Both these trials make the interpretation of benefit difficult as everyone receives the active treatment.

The baricitinib trial was extremely underpowered with a total of only 15 patients with active dermatomyositis or polymyositis with failure of glucocorticoids and at least 1 immune suppressive drug. The 2 groups were not compared and since both arms received baricitinib (Group 1 had 24 weeks of active treatment from randomisation with 12 weeks follow-up (immediate start arm), whereas Group 2 had 12 weeks of standard of care followed by 24 weeks active treatment (delayed-start arm).). Unless there was a thought that baricitinib would be markedly different between the 2 groups, the study design doesn’t make sense to me. Also, any power calculation comparing the same drug in both arms would need likely hundreds of patients to demonstrate a difference between starting baricitinib in both groups; one with a 12 week delay. The primary outcome should have been at the time that Group 2 started baricitinib (ie at 12 weeks).

So, what can we conclude? Ultimately, it’s hard to draw firm conclusions, but the combined responses looked good.

1.Beckett M, Tan J, Bonnardeaux E, et al. Tofacitinib therapy in refractory myositis:  a retrospective cohort study of 41 patients. heumatology (Oxford). 2024 May 2;63(5):1432-1436.

2. Chinoy h, Krishan A, Sylvestre Y, Lilleker J, Gordon P, Tansley S, Prabu A, Aslam A, Snedden A,Lamb J. Baricitinib in the Treatment of Adult Idiopathic Inflammatory Myopathy: A Randomized,Treatment Delayed-Start Clinical Trial [abstract]. Arthritis Rheumatol. 2024; 76 (suppl 9).https://acrabstracts.org/abstract/baricitinib-in-the-treatment-of-adult…. Accessed October 23, 2024.

3. Oddis CV, Reed AM, Aggarwal R, et al. Rituximab in the treatment of refractory adult and juvenile dermatomyositis and adult polymyositis: a randomized, placebo-phase trial. Arthritis Rheum. 2013 Feb;65(2):314-24.