A Study to Evaluate the Efficacy and Safety of Proximod in Patients With Rheumatoid Arthritis

Inclusion Criteria: * According to the 2010 classification criteria for rheumatoid arthritis (RA) of the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR), the diagnosis is made for RA and the disease duration at the screening visit is at least 3 months. * Moderate to severe RA defined by 6 or more tender joints, 6 or more swollen joints (68- or 66-joint count), and an ESR of 28 mm/h or greater or hsCRP \> 1.2 × upper limit of laboratory normal range (ULN). * Before the first administration, the participants had received MTX treatment for at least 3 consecutive months, with a stable dose for at least 4 weeks (oral or parenteral MTX \[10-25 mg/week; or for those who were intolerant to the maximum dose of ≥10 mg/week, a dose of ≥7.5 mg/week could be used\]). * The participants had previously received at least one form of bDMARDs and/or tsDMARDs, but the treatment was either ineffective or they experienced intolerability. Ineffectiveness is defined as: After continuous treatment with the same bDMARD or tsDMARD for at least 12 weeks, there is still persistent or recurrent disease activity of rheumatoid arthritis, or the initial clinical improvement achieved during the treatment subsequently weakens or disappears, and the study investigator determines that the expected treatment goal has not been reached, thus requiring discontinuation or replacement of the drug. Intolerance is defined as: Those who have actually received treatment with a certain bDMARD or tsDMARD in the past and permanently discontinued the treatment due to recorded adverse events related to the drug, abnormal and clinically significant laboratory tests, or other toxicities, and the study investigator determines that continued use or re-use of the drug is not appropriate. Those who discontinue the treatment due to intolerance do not require a treatment duration of at least 12 weeks. * Participants used a stable dose of oral/inhaled prednisone (≤ 10 mg/day) or an equivalent dose of glucocorticoids 4 weeks before the first administration of the study drug, and were expected to continue using the original stable dose during the trial; or they had stopped using oral/inhaled glucocorticoids ≥ 2 weeks before the first administration. * Participants used a stable dose of non-steroidal anti-inflammatory drugs or acetaminophen/paracetamol 4 weeks before the first administration of the study drug, and were expected to continue taking the original stable dose during the trial; or they had stopped using non-steroidal anti-inflammatory drugs or acetaminophen/paracetamol for ≥ 5 half-lives/2 days (whichever was the longer period). * During the course of the study and within 9 months after the last administration of the study drug, all female and male participants of reproductive age must use appropriate contraceptive measures. Exclusion Criteria: * Known or suspected allergies to the study drug or any component of the study drug. * The ACR functional classification is level IV. * Those who have been bedridden for a long time or are confined to a wheelchair for a long period of time. * The participants plan to undergo joint surgery or major surgeries during the treatment period. * During the screening, if the participant's forced expiratory volume in one second (FEV1) or forced vital capacity (FVC) was lower than 70% of the predicted value, and the FEV1/FVC ratio was less than 0.70; * During the 4 weeks prior to the first administration of the drug, the following medications or treatments were used: Glucocorticoids: Administration can be through intra-articular injection, at trigger points or tender points, within the joint capsule, within the tendon sheath, or by intramuscular or intravenous injection. Other DMARDs except MTX: including but not limited to minocycline, penicillamine, sulfasalazine, hydroxychloroquine, chloroquine, azathioprine, gold preparations, cyclophosphamide, Tripterygium wilfordii(Leigongteng), ilarimod. Immunosuppressive or immunomodulatory drugs: including but not limited to tacrolimus, cyclosporine, Pavlin(Total Glucosides of Paeony Capsules), mycophenolate mofetil, 6-mercaptopurine, etc. Interferons: including but not limited to interferon, intron A(Interferon alfa-2b injection), Rebetron, etc.; Imaging agents: technetium \[99Tc\] methylenediphosphonate injection; Opioid drugs: including but not limited to oxycodone, oxymorphone, fentanyl, levorphanol, buprenorphine, methadone, hydrocodone, morphine, pethidine; Oral traditional Chinese medicines for treating RA and other inflammatory response diseases (Appendix 9. Traditional Chinese patent medicines related to RA). Received live vaccines or attenuated live vaccines. Undergone major surgery. * Before the first administration of the study drug, any of the following drugs or treatments were used: * Received integrin αV antibody or cell depletion therapy within 5 half-lives or within 3 months (whichever is longer). * Used drugs that interact with the study drug within 5 half-lives or within 4 weeks (whichever is longer). See Table 12-3. * Received JAK inhibitors and/or S1P receptor agonists within 5 half-lives or within 2 weeks (whichever is longer). * Took oral or intravenous anti-infective drugs within 14 days. * Have used any type of leukopoietic agents within the past 14 days. * Used leflunomide within 12 weeks; if standard colestyramine (8g, 3 times daily) is used to elute leflunomide, it needs to be eluted for 11 days, and the eluting drug should be discontinued for ≥ 2 weeks before the first administration of the study drug. * The withdrawal requirements for biologic disease-modifying antirheumatic drugs (bDMARDs) are shown in Table 12-4. * Within 3 months prior to randomization: * Has participated in any interventional clinical trials involving drugs or medical devices. * Has donated blood and the volume of donation was ≥ 400 mL, or has received blood transfusion. * Alcohol abuse (i.e., consumption of more than 14 standard units per week \[a standard unit containing 14 g of alcohol, such as 360 mL of beer or 45 mL of 40% liquor or 150 mL of wine\]) or substance abuse was present at screening or had a history of alcohol abuse or substance abuse within 6 months before randomization. * Patients with active tuberculosis, positive γ-interferon release assay (T-SPOT.TB or other γ-interferon release assay equivalent indicators) by chest CT examination during screening. * Potential malignancy was present at the time of screening. * Ophthalmologic studies, including fundus examination and optical coherence tomography, were abnormal and clinically relevant at screening, especially for participants with macular disorders and maculopathy. * Participants who are pregnant or breastfeeding, or those who plan to become pregnant or breastfeed during the course of the study or within 9 months after the last administration of the drug. * The investigator considered that there were any other factors that might affect the conduct of the study or the evaluation of outcomes.