On October 22, 2025 Kyowa Kirin International (KKI), a wholly owned subsidiary of Kyowa Kirin Co., Ltd. (TSE:4151, Kyowa Kirin), a Japan-based global specialty pharmaceutical company, and the University Hospitals Birmingham NHS Foundation Trust, reported new overall survival (OS) insights from the PROCLIPI (PROgnostic Cutaneous Lymphoma International Prognostic Index) Study aligning with previous findings that suggest mogamulizumab may offer meaningful OS benefit for patients living with mycosis fungoides (MF) and Sézary syndrome (SS), two rare conditions and subtypes of cutaneous T-cell lymphoma (CTCL).

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Key findings2:

For patients with advanced-stage MF and SS (n=371), the median overall survival from the onset of treatment was higher for patients treated with mogamulizumab (n=72) at 64 months compared with those not receiving mogamulizumab (n=175) at 54 months (p<0.01).
Patients treated with mogamulizumab showed a trend toward improved OS compared to those not receiving mogamulizumab across risk-stratified groups according to the new Cutaneous Lymphoma International Prognostic Index (CLIPI).
For a subset of patients with SS (n=96), the median OS is around 6.5 years for patients treated with mogamulizumab (n=46) compared with around 3 years for systemic treatment but not mogamulizumab (n=50) (p<0.01).
This research was presented as part of the Scientific Proceedings at this year’s European Organisation for Research and Treatment of Cancer Cutaneous Lymphoma Tumour Group (EORTC-CLTG) Annual Meeting in Athens, Greece.2 The data contributes to a growing body of evidence suggesting potential OS benefits with mogamulizumab, 4,5 highlighting the importance of collaboration across the CTCL community in advancing understanding of survival outcomes and helping to shape the future of patient care.

"The PROCLIPI Study demonstrates the power of global collaboration in rare diseases. By bringing together data from across the world, we can generate insights that simply wouldn’t be possible in isolation," says Professor Julia Scarisbrick, Chief Investigator of the PROCLIPI Study and Honorary Professor of Dermatology, University Hospitals Birmingham NHS Foundation Trust. "We are proud to coordinate this initiative as we’re working to build rigorous scientific evidence while giving patients and their families a better understanding of what long-term survival looks like."

The PROCLIPI Study, now in its tenth year, aims to develop prognostic indices for MF and SS. The study collects comprehensive data, including clinical, haematological, pathological, imaging, treatment with responses, quality of life and survival data.1 Recently, a new prognostic index (CLIPI) for advanced CTCL was published to enable precise patient risk stratification.6

"For those of us in the CTCL community, survival isn’t just about numbers on a chart – it’s about being able to spend more time with our families, plan for the future, and live life with dignity", says Susan Thornton, CEO, Cutaneous Lymphoma Foundation. "That’s why initiatives like PROCLIPI are important, as the data collected reflects real lived experiences and can help inform future improvements in care for patients."

The independent international PROCLIPI Study aligns with Kyowa Kirin International’s commitment to generating real-world insights that advance the understanding of CTCL and turn these clinical insights into meaningful improvements in access, policy, and patient care.

Cutaneous T-cell lymphoma is a rare disease7, and innovation in this environment can be challenging due to the rarity of this disease.8 Yet despite these challenges, mounting evidence continues to emerge4,5 to help strengthen our collective understanding of potential treatment benefits.

"These insights into improved overall survival for patients living with CTCL mark an important step forward, providing a stronger clinical evidence base and reinforcing the value of international networks in rare disease research," says Dr Nick Kronfeld, Head of Medical Affairs, Kyowa Kirin International. "By working alongside scientific and patient communities in CTCL, we can gain a better understanding of real-world outcomes, enabling us to bring life-changing value to patients and families, not just today but over the long term."

Note to editors

The OS data from the PROCLIPI Study was presented as an oral presentation during the EORTC CTCL Annual Group Meeting 2025.2 KKI did not sponsor the PROCLIPI study or OS analysis.
The median OS for patients (n=72) receiving mogamulizumab compared to those not receiving mogamulizumab (n=175) was 64 months versus 54 months.2
Median OS data amongst risk stratifications according to CLIPI: 2,6
Low-risk: 67 months vs. ‘not reached’ for mogamulizumab versus those who had not received mogamulizumab
Medium-risk: 64 vs. 48 months for mogamulizumab versus those who had not received mogamulizumab
High-risk: 26 vs. 13 months for mogamulizumab and for those who had not received mogamulizumab

(Press release, Kyowa Hakko Kirin, OCT 22, 2025, View Source [SID1234656914])