Biosimilar CT-P43 Matches Ustekinumab in Treating Moderate to Severe Plaque Psoriasis

This article was originally published on AJMC®.

A new phase 3 clinical trial suggests that CT-P43, a biosimilar for the widely used biologic ustekinumab (Stelara; Johnson & Johnson), yields comparable efficacy, safety, and immunogenicity in patients with moderate to severe plaque psoriasis.1

The findings support the use of CT-P43, approved in the US as Steqeyma (Celltrion) in 2024,2 as an alternative treatment option to biologic therapies for individuals living with the chronic inflammatory skin disease. These long-term findings were recently published in Dermatologic Therapy.1

Results showed that CT-P43 met the criteria for equivalence with the reference ustekinumab therapy. | Image credit: © SergeVo - stock.adobe.com

Moderate to severe forms of psoriasis often require systemic therapy, including biologic agents that target key immune pathways. However, biologics remain costly, and biosimilars are increasingly being developed to improve affordability and access to treatment.

Ustekinumab, a monoclonal antibody that blocks the IL-12 and IL-23 pathways, has become a widely used treatment for psoriasis due to its strong clinical efficacy and relatively infrequent dosing schedule.

The randomized, double-blind, multicenter phase 3 trial evaluated the efficacy and safety of CT-P43 compared with ustekinumab in adults with moderate to severe plaque psoriasis who were eligible for systemic therapy or phototherapy. The study enrolled more than 500 patients across multiple countries, randomly assigning them to receive either treatment with a primary endpoint of proportion of patients achieving at least a 75% improvement in the Psoriasis Area and Severity Index (PASI 75) at week 12—a widely used benchmark for evaluating psoriasis treatment efficacy.

Participants received treatment according to the standard ustekinumab dosing schedule, which includes initial doses at week 0 and week 4 followed by maintenance dosing every 12 weeks. Patients were monitored for clinical response, safety outcomes, and immune reactions throughout the study period.

Results showed that CT-P43 met the criteria for equivalence with the reference ustekinumab therapy. The proportion of patients achieving PASI 75 at week 12 was highly similar between the 2 treatment groups, falling within the predefined equivalence margin established by the study researchers.

The researchers noted that improvements in PASI scores were maintained through week 52, with improvements remaining comparable between the 2 groups. PASI 50, 75, and 90 rates at week 52 among patients who continued receiving CT-P43 were 93.3%, 89.3%, and 79.4%; among those who continued receiving ustekinumab were 94.4%, 92.8%, and 81.6%; and among those who switched to CT-P43 were 96.0%, 89.5%, and 76.6%.

“Maintenance of PASI responses for up to 1 year aligns with long-term findings from studies with reference ustekinumab,” wrote the group. “Some patients who did not initially respond at Week 12 showed improvement in PASI with continued treatment, suggesting that initial nonresponders may show improvement with continued therapy.”

Secondary end points reinforced these findings. Comparable proportions of patients receiving CT-P43 and reference ustekinumab achieved more stringent measures of skin clearance, including PASI 90 and PASI 100 responses, which represent near-complete or complete resolution of psoriasis lesions.

Safety outcomes were also consistent between the 2 groups. The overall incidence of treatment-emergent adverse effects was similar for patients receiving CT-P43 and those receiving the reference biologic. Most adverse effects were mild to moderate in severity and aligned with the known safety profile of ustekinumab.

Immunogenecity findings showed that rates of antidrug antibody formation were comparable between the CT-P43 and reference ustekinumab groups, suggesting that the biosimilar does not introduce additional immune-related risks.

Researchers also assessed the impact of switching treatments during the study. A subset of patients who initially received ustekinumab were transitioned to CT-P43 later in the trial. Clinical responses remained stable following the switch, and no new safety concerns emerged, supporting the interchangeability of the biosimilar with ustekinumab.

References

1. Papp KA, Jaworrski J, Kwiek B, et al. Efficacy and safety of CT-P43, a candidate ustekinumab biosimilar, in moderate-to-severe plaque psoriasis: 52-week results from a randomised, active-controlled, double-blind, phase 3 study. Dermatol Ther. Published online February 23, 2026. doi:10.1155/dth/8811546

2. U.S. FDA approves Celltrion's STEQEYMA (ustekinumab-stba), a biosimilar to STELARA (ustekinumab). News release. Celltrion. December 18, 2024. Accessed March 13, 2026. https://www.celltrionusa.com/board/newslist/29