Psoriasis is a chronic immune-mediated inflammatory skin disease driven largely by the interleukin (IL)-23/Th17 signaling axis, a pathway that modern immunology has identified as a central engine of the disease’s characteristic plaques and systemic inflammation. Tildrakizumab is a humanized monoclonal antibody engineered to bind selectively to the p19 subunit of IL-23, thereby interrupting IL-23-dependent Th17 responses while leaving upstream immune pathways largely intact. This selectivity is the drug’s conceptual appeal: it suppresses the pathogenic inflammation at the heart of psoriasis without the broader immune perturbation associated with agents that directly inhibit IL-17 or other cytokines.

The drug’s pedigree in trials is strong. In the pivotal phase III studies reSURFACE 1 and reSURFACE 2, tildrakizumab demonstrated robust efficacy and a favorable long-term safety profile in patients with moderate-to-severe plaque psoriasis, and a Japanese subgroup analysis plus a five-year extension study confirmed durable efficacy and tolerability in Japanese patients specifically. But trial populations are highly selected, and the gap between trial conditions and routine practice is precisely where real-world evidence becomes indispensable. Differences in baseline disease severity, prior treatments, and how outcomes are counted can dramatically reshape the apparent success of a therapy.

The Iwate team took a deliberately conservative approach. Between July 2021 and December 2025, 49 patients initiated tildrakizumab at their center; after excluding 8 patients treated without the approved loading regimen, 10 who had not yet reached 28 weeks of treatment, and 1 treated outside the approved dosing interval, 30 consecutive patients formed the analysis cohort. All received tildrakizumab 100 mg according to the approved Japanese regimen: subcutaneous injections at weeks 0 and 4, followed by maintenance dosing every 12 weeks. Disease severity was tracked with the Psoriasis Area and Severity Index (PASI) at weeks 0, 4, 16, 28, 40, and 52, with a visit window of plus or minus one week.

The cohort itself reflects the messy reality of dermatology clinics. The 30 patients included 22 men and 8 women, with a mean age of 57.3 years ranging from 26 to 81, a mean body weight of 69.44 kilograms, and a mean disease duration of 17.4 years. Twelve patients had a body mass index of 25 or higher, and 21 were current or former smokers. Thirteen had lived with psoriasis for at least two decades. Only five patients had prior exposure to biologic therapy, four with ustekinumab and one with risankizumab, while 25 were biologic-naïve. Half had previously tried apremilast, and nearly all used concomitant topical therapy. Notably, no patients discontinued treatment before week 28 among those included in the analysis.

The effectiveness data tell a story of rapid improvement followed by sustained consolidation. The mean PASI score fell from 11.45 at baseline, with a median of 9.2, to 7.79 at week 4, 4.69 at week 16, 3.71 at week 28, 3.53 at week 40, and 2.90 at week 52. The steepest decline occurred in the early treatment phase, particularly by week 16, after which scores continued to drift downward or held steady through the maintenance phase. This pattern suggests that tildrakizumab induces a rapid initial response that is then maintained with continued dosing in routine clinical practice, exactly the profile clinicians hope for in a disease requiring lifelong management.

Responder analyses added a crucial layer of rigor. The researchers applied non-responder imputation (NRI), a conservative method in which patients who discontinued treatment or had missing PASI data are classified as non-responders at subsequent visits. Under this approach, PASI75 achievement, meaning a 75 percent reduction in disease severity, rose from 3.3 percent at week 4 to 36.7 percent at week 16, 46.7 percent at week 28, 50.0 percent at week 40, and 56.7 percent at week 52. Absolute disease control, defined as a PASI score of 3 or less, followed a similar trajectory, reaching 60.0 percent at week 52 with a 95 percent confidence interval of 42.3 to 75.4. As-observed rates, which count only evaluable patients, were higher still, at 68.0 percent for PASI75 and 72.0 percent for PASI ≤3 at week 52.

Four patients stopped treatment because of insufficient efficacy, with final PASI scores of 7.5 at week 4, 1.6 at week 16, 3.7 at week 28, and 3.2 at week 40; two subsequently switched to another biologic and two returned to conventional systemic or topical therapy. The remaining 26 patients, or 86.7 percent of the cohort, continued treatment through week 52. Safety was assessed retrospectively from electronic medical records rather than through protocolized surveillance, a limitation the authors acknowledge candidly. Seven adverse events were documented, including low back pain associated with spinal canal stenosis, injection-site erythema, facial erythema, pruritus, hyperlipidemia, chest tightness, and vesicular eruptions on the hands and feet, one event each. Critically, no treatment discontinuations related to adverse events occurred.

How do these numbers compare with European real-world studies? The picture is heterogeneous, and the authors argue the discrepancies are more plausibly attributable to methodology than to true differences in drug performance. The Italian IL-PSO multicenter retrospective study reported PASI75 rates approaching 90 percent at week 52, while a German retrospective multicenter analysis over 76 weeks reported PASI75 in 85.5 percent and absolute PASI below 3 in 79.7 percent. A large Basque Country cohort of 212 patients reported PASI75 in 66.4 percent and PASI ≤3 in 68.8 percent. The Iwate cohort’s lower PASI75 rate likely reflects its relatively low baseline mean PASI of 11.45, compared with 16.0 in the German TILOT study and 14.45 in IL-PSO, combined with the conservative NRI approach. In cohorts with lower baseline severity, relative thresholds like PASI75 are mathematically harder to reach, whereas absolute measures such as PASI ≤3 may better capture meaningful disease control.

The exploratory subgroup analyses yielded one intriguing signal. At week 52, non-smokers showed a numerically higher PASI ≤3 achievement rate than current or former smokers, 88.9 percent versus 47.6 percent, an association that reached nominal significance in unadjusted analysis with a p value of 0.049 but dissolved after Holm adjustment for multiple comparisons across 20 subgroup tests, yielding an adjusted p value of 0.984. No other baseline factors, including sex, body mass index, age, or disease duration, showed significant differences. The authors frame the smoking finding as hypothesis-generating, noting that smoking has been reported to adversely affect biologic treatment response in psoriasis, and they emphasize that the retrospective single-center design, small sample size, and lack of confounder adjustment demand caution. Older patients aged 65 and above responded comparably, consistent with prior real-world studies of tildrakizumab in elderly populations. Taken together, the study bridges Japanese trial data and everyday practice, suggesting that for many patients the realistic therapeutic goal is not dramatic relative improvement but stable, low absolute disease activity sustained over the long haul.

Subject of Research: Real-world effectiveness and safety of the interleukin-23 p19 inhibitor tildrakizumab in Japanese patients with plaque psoriasis over 52 weeks

Article Title: Real-world effectiveness and safety of tildrakizumab in Japanese patients with psoriasis: a single-center 52-week observational study

Article References: Watabe, D., Tsunoda, K., Hamabata, A., Goto, M., Yoshioka, W., & Amano, H. (2026). Real-world effectiveness and safety of tildrakizumab in Japanese patients with psoriasis: a single-center 52-week observational study. Journal of Cutaneous Immunology and Allergy, 9, Article 16442. https://doi.org/10.3389/jcia.2026.16442

Image Credits: AI Generated

DOI: 10.3389/jcia.2026.16442

Keywords: tildrakizumab, psoriasis, interleukin-23, real-world evidence, biologic therapy, PASI, Japan, dermatology, Th17 axis, drug safety, observational study, immunology