MOSAIC updates: MRI outcomes bolster apremilast role in PsA dactylitis

Apremilast, an oral immunomodulating phosphodiesterase-4 inhibitor, reduces inflammation in individual joints and clinical dactylitis as per MRI in patients with psoriatic arthritis (PsA), according to the results of a dynamic contrast-enhanced MRI (DCE-MRI) analysis of the phase IV, open-label MOSAIC study.

The findings come on the heels of the primary analysis results showing improved measures of inflammation in patients with PsA following apremilast treatment, according to the PsA MRI Scoring of the hand and the MRI Whole-Body Scoring System for Inflammation in Peripheral Joints and Entheses. [Lancet Rheumatol 2025;7:e118-e126]

“[We also conducted] optional DCE-MRI … in most cases. DCE-MRI is a highly sensitive technique that allows for evaluation of perfusion through automated quantification of gadolinium contrast agent uptake within the synovial membrane and bone marrow, thereby estimating the degree of joint inflammation,” the researchers explained. [Acad Radiol 2007;14:1189-1200]

A total of 122 participants (mean age 46.6 years, 54.9 percent women) received apremilast 30 mg BID with or without stable methotrexate for up to 48 weeks. About 42 percent were on concomitant methotrexate (mean dose 4.7 mg/week). DCE-MRI was performed at baseline in 110 patients and at weeks 24 and 48. [EULAR 2025, abstract POS1345]

In the predefined DCE-MRI analysis, there were no statistically significant changes in the mean results of all-joint data. According to the investigators, this may have been driven by a diluting effect from non-affected joints.

However, when looking at the most-affected joints based on DCE-MRI Quantification (DEMRIQ) values at baseline, there were significant reductions in mean DEMRIQ-VOL* and DEMRIQ-ME* scores from baseline for the most-affected DIP, PIP, and MCP** joints at weeks 24 and 48, the investigators pointed out.

In the ModDA*** subset (n=53), the mean changes in DEMRIQ-Vol from baseline at week 24 for the most-affected DIP, PIP, and MCP joints were -0.07, -0.07, and -0.09 mL, respectively. The corresponding week-48 values were -0.06, -0.04, and -0.08 mL. For DEMRIQ-ME, the reductions for the most-affected joints were -0.1 (DIP) and -0.15 (PIP) mL at week 24, and -0.11 and -0.12 mL, respectively, at week 48. According to the investigators, these mean changes were statistically significant based on p-values of <0.05.

In the HDA*** population (n=53), the researchers noted statistically significant or numerical reductions in DEMRIQ-Vol and DEMRIQ-ME for all the most-affected joints at weeks 24 and 48.

For DEMRIQ-IRE*, the improvements across all joints were modest but failed to achieve statistical significance for both ModDA and HDA subsets.

In patients with dactylitis at baseline (n=45; mean LDI^# 39.7), there were statistically significant reductions in LDI from baseline at weeks 24 and 48 (least-squares mean -34.38 and -38.71, respectively). At week 48, the dactylitis count in all but two of 30 patients was 0.

About 12 percent of participants experienced treatment-emergent adverse events (TEAEs) that led to study drug discontinuation. The most common TEAEs were diarrhoea (33.6 percent), nausea (12.3 percent), and headache (10.7 percent). The incidences of severe and serious TEAEs were low (4.9 percent for both).

Takeaways

“In patients with PsA treated with apremilast, individual joint inflammation assessed by DCE-MRI significantly decreased from baseline to weeks 24 and 48 in all the most-affected DIP, PIP, and MCP joints,” the investigators noted.

“These data demonstrate the value of DCE-MRI technology for targeted analysis and indicate a treatment-induced reduction in inflammation in the joints most severely affected by inflammation in PsA,” they added.