Introduction: For patients with rheumatoid arthritis (RA) unresponsive to first-line biologic/targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs), the selection of second-line b/tsDMARDs is crucial to prevent progression to difficult-to-treat rheumatoid arthritis (D2TRA). However, indicators for selection are lacking. This study aimed to identify optimal second-line b/tsDMARDs among the phase III treatment strategies based on European League Against Rheumatism (EULAR) RA management recommendations., Methods: A total of 687 RA patients treated with second-line b/tsDMARDs (tumor necrosis factor inhibitor (n = 246), interleukin-6 receptor inhibitor [n = 195], cytotoxic T-lymphocyte-associated protein 4 immunoglobulin [n = 119], and Janus kinase inhibitor [n = 127]) were enrolled between October 2013 and April 2023. Rates of patients achieving Clinical Disease Activity Index (CDAI) remission and CDAI low disease activity (LDA), changes in CDAI, persistence rates, and adverse events within 24 weeks after treatment initiation were compared among the four groups. Propensity score-based inverse probability of treatment weighting (PS-IPTW) was used to minimize selection bias., Results: After PS-IPTW adjustment, the Janus kinase inhibitor (JAKi) group had the highest persistence rate among the four groups. At 24 weeks, the JAKi group showed the greatest improvement in CDAI and the highest CDAI remission rate. Among patients treated with JAKi as second-line b/tsDMARDs, upadacitinib (UPA) was most likely to achieve CDAI remission at 24 weeks. The comparison between the UPA group (n = 32) and the non-UPA JAKi group (tofacitinib and baricitinib [n = 95]) showed comparable persistence rates but significantly lower CDAI scores and higher CDAI remission rate at 24 weeks in the UPA group. No significant difference was noted in the overall incidence of adverse events among the four groups treated with b/tsDMARDs or between the groups treated with JAKi., Conclusions: Selecting JAKi, especially UPA, may effectively improve the disease activity for RA patients unresponsive to first-line b/tsDMARDs. Further large-scale studies are needed to clarify the efficacy and safety of UPA., Trial Registration: FIRST registry (approval number#04-23): October 2013, retrospectively registered., Competing Interests: Declarations. Conflict of Interest: Yusuke Miyazaki has received consulting fees, speaking fees, lecture fees, and/or honorariums from AstraZeneca, GlaxoSmithKline, Bristol-Myers, Astellas, Asahi-kasei, AbbVie, Chugai, Sanofi, Eisai, Eli Lilly, and Boehringer Ingelheim. Shingo Nakayamada has received consulting fees, speaking fees, lecture fees, and/or honorariums from AstraZeneca, GlaxoSmithKline, Pfizer, Bristol-Myers, Astellas, Asahi-kasei, AbbVie, Chugai, Sanofi, Eisai, Gilead Sciences, Mitsubishi-Tanabe, Janssen, Eli Lilly, Boehringer Ingelheim and Ayumi. Satoshi Kubo has received speaking fees from Eli Lilly, GlaxoSmithKline, Bristol-Myers, AbbVie, Eisai, Pfizer, AstraZeneca and also research grants from Daiichi-Sankyo, AbbVie, Boehringer Ingelheim, and Astellas. Masanobu Ueno has received speaking fees from GlaxoSmithKline. Yoshiya Tanaka has received speaking fees and/or honorariums from Gilead Sciences, AbbVie, Boehringer Ingelheim, Eli Lilly, Mitsubishi-Tanabe, Chugai, Amgen, YL Biologics, Eisai, Astellas, Bristol-Myers, and AstraZeneca; received research grants from Asahi-Kasei, AbbVie, Chugai, Mitsubishi-Tanabe, Eisai, Takeda, Corrona, Daiichi-Sankyo, Kowa, and Boehringer Ingelheim; and received consultant fees from Eli Lilly, Daiichi-Sankyo, Taisho, Ayumi, Sanofi, GlaxoSmithKline, and AbbVie. Ryuichiro Kanda, Shunsuke Fukuyo, Ippei Miyagawa, Ayako Yamaguchi, Yurie Satoh-Kanda, Naoaki Ohkubo, Yasuyuki Todoroki, Hiroaki Tanaka, Atsushi Nagayasu, Yuya Fujita, Takafumi Aritomi, Katsuhide Kusaka, Hidenori Sakai, Satsuki Matsunaga, and Hirotsugu Nohara have nothing to disclose. Yoshiya Tanaka is an Editorial Board member of Rheumatology and Therapy. Yoshiya Tanaka was not involved in the selection of peer reviewers for the manuscript nor any of the subsequent editorial decisions. Ethical Approval: This study was approved by the ethics review board of the University of Occupational and Environmental Health, Japan (approval number #04-23). The FIRST registry includes RA patients who initiated treatment with b/tsDMARDs. Informed consent was obtained from all patients who have consented to the FIRST registry., (© 2025. The Author(s).)