CT-P43 Matches Ustekinumab Through 52 Weeks in Psoriasis

Long-term results from a phase 3 trial evaluating CT-P43, a biosimilar to ustekinumab, support sustained equivalence in efficacy, pharmacokinetics, safety, and immunogenicity through 52 weeks in adults with moderate to severe plaque psoriasis.¹

Ustekinumab, a monoclonal antibody targeting the IL-12/23 p40 subunit, remains a well-established biologic therapy for plaque psoriasis.² However, cost considerations and access barriers continue to influence treatment decisions. The availability of biosimilars such as CT-P43 may help address these challenges while maintaining comparable clinical outcomes.

Earlier findings from this randomized, double-blind phase 3 study (NCT04673786) demonstrated equivalence between CT-P43 and European Union–sourced reference ustekinumab for the primary end point of mean percent improvement in Psoriasis Area and Severity Index (PASI) at week 12. The newly reported data extend through the week 52 end-of-study visit, including outcomes in patients who continued CT-P43, continued reference ustekinumab, or switched from reference therapy to CT-P43 at week 16.

Study Overview

The trial enrolled adults aged 18 to 80 years with moderate to severe plaque psoriasis (PASI ≥ 12, ≥ 10% body surface area involvement, static Physician Global Assessment [sPGA] ≥ 3). Patients had not previously received IL-12/23 inhibitors, including ustekinumab.

Patients were randomly assigned 1:1 to receive CT-P43 or reference ustekinumab at weeks 0 and 4. Dosing was based on weight (45 mg for ≤ 100 kg; 90 mg for > 100 kg). At week 16, patients originally assigned to reference ustekinumab were again randomly assigned to either continue reference treatment or switch to CT-P43. Those initially receiving CT-P43 continued on the biosimilar.

A total of 502 patients entered the second treatment period, and completion rates exceeded 94% across groups, supporting the robustness of the 1-year data.

Efficacy Maintained Through 1 Year

Clinical responses observed at week 12 were sustained through week 52 across all treatment arms.

Absolute PASI scores remained low and stable between weeks 40 and 52, with minimal numerical differences between groups. At week 52:

• PASI 75 was achieved by:
  • 89.3% continuing CT-P43
  • 92.8% continuing reference ustekinumab
  • 89.5% switching to CT-P43
• PASI 90 responses were similarly comparable:
  • 79.4% (CT-P43 continuation)
  • 81.6% (reference continuation)
  • 76.6% (switch group)

More than 93% of patients in each group achieved PASI 50 at week 52.

Importantly, some patients who did not achieve PASI 50 at week 12 went on to achieve PASI 75 by week 52, suggesting that continued therapy may yield benefit in select early nonresponders.

Improvements in sPGA paralleled PASI results. By week 40, more than 80% of patients achieved clear or almost clear skin (sPGA 0/1), and these responses were maintained through week 52.

Quality-of-life improvements were also durable. Mean Dermatology Life Quality Index (DLQI) reductions exceeded 8 points across groups, and most patients achieved DLQI 0/1 at later visits.

Switching from reference ustekinumab to CT-P43 at week 16 did not result in loss of efficacy.

Pharmacokinetics Consistent Across Groups

Serum ustekinumab concentrations at weeks 40 and 52 were generally similar across all groups, including those who transitioned to CT-P43.

Higher serum concentration quartiles were associated with numerically greater PASI improvements, and this trend was consistent regardless of treatment assignment. Switching did not meaningfully alter drug exposure.

Safety Profile Aligns With Established Experience

The safety findings over 52 weeks were consistent with the known safety profile of ustekinumab.

During treatment period 2 and follow-up, 37.6% of patients experienced at least 1 treatment-emergent adverse event (TEAE), with comparable rates across groups. Most events were mild or moderate in severity.

COVID-19 was the most frequently reported TEAE, reflecting the timing of the study during the pandemic. Upper respiratory tract infections were also common. Latent tuberculosis was identified through protocol-mandated screening; no cases of active tuberculosis occurred.

Serious adverse events were infrequent and distributed evenly. One death due to myocardial infarction occurred in a patient receiving CT-P43 and was not considered related to the treatment. One case of tubular breast carcinoma in a patient continuing CT-P43 was considered possibly related by the investigator, but no clustering of malignancies was observed.

Rates of infections, injection site reactions, and hypersensitivity were similar between continued and switched patients. No new or unexpected safety signals emerged after switching.

Immunogenicity Findings Reassuring

Across the overall study period, fewer patients receiving CT-P43 had antidrug antibody (ADA) positivity compared with those receiving reference ustekinumab. After week 16, ADA and neutralizing antibody rates were similar between patients who continued reference therapy and those who switched to CT-P43.

Although ADA-positive patients tended to have slightly lower serum drug concentrations, there was no meaningful impact on efficacy or safety. No association was observed between antibody status and adverse events, injection site reactions, or hypersensitivity.

Switching to CT-P43 did not increase immunogenicity risk.

Clinical Takeaway

The 52-week results reinforce previously demonstrated equivalence between CT-P43 and reference ustekinumab in moderate to severe plaque psoriasis.

Efficacy was durable, pharmacokinetics were consistent, and safety and immunogenicity profiles remained comparable, including after a single switch from reference therapy.

For clinicians, these data support CT-P43 as a clinically comparable biosimilar option, offering the potential for increased treatment access without compromising long-term outcomes.

References

1. Papp K, Jaworski 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 III study. Dermatol Ther. 2026. doi:10.1155/dth/8811546
2. Koutruba N, Emer J, Lebwohl M. Review of ustekinumab, an interleukin-12 and interleukin-23 inhibitor used for the treatment of plaque psoriasis. Ther Clin Risk Manag. 2010;6:123-141. doi:10.2147/tcrm.s5599