SEAM-PsA Study - Does Monotherapy MTX Win Despite Losing to Etanercept in Psoriatic Arthritis?

Jack Cush, MD

Feb 12, 2019 2:55 pm

The SEAM-PsA study examined the efficacy of methotrexate (MTX) monotherapy, etanercept (ENT) monotherapy or the combination of MTX and ETN in psoriatic arthritis (PsA) patients and found that ETN monotherapy was equivalent to combination therapy - and that both were superior to MTX alone in clinical (ACR and MDA) and radiographic responses.

Mease and colleagues studied 851 PsA (MTX, ETN, and biologic naive) patients who were randomized to either: oral MTX (N=284), ETN (N=284), or ETN plus MTX (N=283). The primary and secondary outcomes were the American College of Rheumatology (ACR)20 response and Minimal Disease Activity (MDA) response at week 24 were the primary and key secondary endpoints, respectively.

The key results at week 24 were as follows:

	MTX	ETN	MTX+ETN	p value*
ACR20	50.7%	60.9%	65%	0.029
MDA	22.9%	35.9%	35.7%	0.005
ACR50	30.6%	44.4%	45.7%	0.006
ACR70	13.8%	29.2%	27.7%	0.001

* comparison of ETN and MTX monotherapy groups

The etanercept‐containing arms showed less radiographic progression compared with methotrexate monotherapy at week 48.

While there were no significant changes in skin involvement in those with ≥ 3% BSA at baseline, those with ≥ 10% BSA were more likely to achieve clear or almost clear status by week 24 on ETN monotherapy or combination therapy (compared to MTX monotherapy).

Historically, MTX has been forced as first-line therapy in PsA; a recommendation based more on economics than data.

Moreover there appears to be no benefit of adding MTX to ETN when ETN is used.

This study did not evaluate the most appropriate therapy for those PsA patients who fail to respond to methotrexate, but does suggest that a TNF inhibitor (etanercept) would be the next best option.

https://onlinelibrary.wiley.com/doi/abs/10.1002/art.40851?af=R

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Perhaps the results would have been different if the 'optimal' dosing strategy had been applied. Some would consider MTX 25mg sc, to a more appropriate comparator; I do acknowledge that most RCT's do not utilize 'optimal dosing' of MTX, despite most guidelines supporting their use. Unfortunately, statements by bodies such as NICE, that do not endorse MTXsc, are based on the absence of RCT's to determine/demonstrate its efficacy.