AimsTo investigate the exposure-response (E-R) relationship, including exposure-efficacy and exposure-safety, of ropeginterferon alfa-2b treatment in patients with polycythaemia vera (PV).MethodsBased on the results of the phase II trial A20-202 regarding ropeginterferon alfa-2b in patients with PV, E-R analyses were performed to evaluate the efficacy and safety of the given dosing regimen. The E-R analyses were based on logistic and linear regression and the relationship between exposure to ropeginterferon alfa-2b and key efficacy and safety variables. The key efficacy variables included complete haematologic response (CHR) and reduction of the driver mutation JAK2V617F. The safety variable was treatment-related adverse events (TRAEs).ResultsA clear relationship between the exposure to ropeginterferon alfa-2b and CHR was observed, with an increase in drug exposure resulting in an increased probability of achieving CHR. Similar CHR probabilities were observed in the third and fourth quantiles of the average concentration at Week 24. The results from the exposure-JAK2V617F model indicated that the JAK2V617F allele burden decreased with increasing exposure to ropeginterferon alfa-2b and baseline body surface area. Exposure-safety analysis revealed a risk of AEs associated with transaminase abnormalities, which were not associated with clinical significance.ConclusionsOur analyses have shown that patients with PV treated with ropeginterferon alfa-2b had an increased probability of achieving CHR and a molecular response with acceptable safety risks at the 250-350-500 mu g titration dosing regimen. This study has provided the relevant data for the application of a biologics licence of ropeginterferon alfa-2b for PV treatment in China.

Background: Polycythemia vera (PV) is a myeloproliferative neoplasm. Ropeginterferon alfa-2b is a new -generation polyethylene glycol -conjugated proline-interferon. It is approved for the treatment of PV at a starting dose of 100 mu g (50 mu g for patients receiving hydroxyurea (HU)) and dose titrations up to 500 mu g by 50 mu g increments. The study was aimed at assessing its efficacy and safety at a higher starting dose and simpler intra-patient dose escalation. Methods: Forty-nine patients with PV having HU intolerance from major hospitals in China were treated biweekly with an initial dose of 250 mu g, followed by 350 mu g and 500 mu g thereafter if tolerated. Complete hematological response (CHR) was assessed every 12 weeks based on the European LeukemiaNet criteria. The primary endpoint was the CHR rate at week 24. The secondary endpoints included CHR rates at weeks 12, 36 and 52, changes of JAK2 V617F allelic burden, time to first CHR, and safety assessments. Results: The CHR rates were 61.2%, 69.4% and 71.4% at weeks 24, 36, and 52, respectively. Mean allele burden of the driver mutation JAK2 V617F declined from 58.5% at baseline to 30.1% at 52 weeks. Both CHR and JAK2 V617F allele burden reduction showed consistent increases over the 52 weeks of the treatment. Twentynine patients (63.0%) achieved partial molecular response (PMR) and two achieved complete molecular response (CMR). The time to CHR was rapid and median time was 5.6 months according to central lab results. The CHRs were durable and median CHR duration time was not reached at week 52. Mean spleen index reduced from 55.6 cm 2 at baseline to 50.2 cm 2 at week 52. Adverse events (AEs) were mostly mild or moderate. Most common AEs were reversible alanine aminotransferase and aspartate aminotransferase increases, which were not associated with significant elevations in bilirubin levels or jaundice. There were no grade 4 or 5 AEs. Grade 3 AEs were reversible and manageable. Only one AE led to discontinuation. No incidence of thromboembolic events was observed. Conclusion: The 250-350-500 mu g dosing regimen was well tolerated and effectively induced CHR and MR and managed spleen size increase. Our findings demonstrate that ropeginterferon alfa-2b at this dosing regimen can provide an effective management of PV and support using this dosing regimen as a treatment option.

Ropeginterferon alfa-2b represents a new-generation pegylated interferon-based therapy and is administered every 2–4 weeks. It is approved for polycythemia vera (PV) treatment in the United States and Europe with a starting dose of 100 µg (50 µg for patients receiving hydoxyurea) and intra-patient dose titrations up to 500 µg at 50 µg increments, which took approximately 20 or more weeks to reach a plateau dose level. This study aimed to assess ropeginterferon alfa-2b at an alternative dosing regimen with a higher starting dose and quicker intra-patient dose titrations, i.e., the 250–350–500 μg schema, in 49 Chinese patients with PV with resistance or intolerance to hydroxyurea. The primary endpoint of the complete hematologic response rate at treatment weak 24 was 61.2%, which was notably higher than 43.1% at 12 months with the approved dosing schema. The JAK2 V617F allele burden decreased from baseline to week 24 (17.8% ± 18.0%), with one patient achieving a complete molecular response. Ropeginterferon alfa-2b was well-tolerated and most adverse events (AEs) were mild or moderate. Common AEs included alanine aminotransferase and aspartate aminotransferase increases mostly at grade 1 or 2 levels. Patients did not present with jaundice or significant bilirubin level increase. No grade 4 or 5 AEs occurred. Seven patients (14.3%) experienced reversible, drug-related grade 3 AEs. No AEs led to treatment discontinuation. Ropeginterferon alfa-2b at the 250–350–500 μg regimen is highly effective and well-tolerated and can help patients achieve greater and rapid complete hematologic and molecular responses. Clinical Trial Registration: This trial is registered at ClinicalTrials.gov (Identifier: NCT05485948) and in China (China National Medical Products Administration Registration Number: CTR20211664).

Ropeginterferon α-2b is a mono-PEGylated proline-interferon for the treatment of polycythemia vera. This drug is used biweekly with a starting dose of 100 μg (50 μg if patients receiving hydroxyurea) and 50 μg increments up to a maximum dose of 500 μg. Increasing evidence indicates that patients can tolerate higher starting doses of ropeginterferon α-2b. This phase II trial utilizes 250 μg as the starting dose, 350 μg at week 2 and 500 μg at week 4 as the target dose. Doses can be adjusted according to tolerability. This study assesses the safety, efficacy and molecular response of ropeginterferon α-2b in Chinese patients with PV utilizing the 250–350–500 μg dosing schema. This study will be used to support the application of a biologics license for polycythemia vera treatment in China.

7062 Background: Currently, ruxolitinib is the only marketed Janus kinase inhibitor (JAKi) for pts with MF in China, which demonstrated symptomatic and splenic benefit with increased cytopenias. However, at least 50% of pts develop resistance or intolerance to ruxolitinib in the long-term follow up, for whom life expectancy is largely reduced. There are few therapeutic options after ruxolitinib failure. Jaktinib, an oral novel JAK and AVCR1 inhibitor showed promising activity in Jaki-naïve pts with intermediate or high risk MF with mild side effects. Here we present the results of jaktinib in MF pts who were refractory or relapsed to prior ruxolitinib therapy. Methods: Pts who had primary or post-ET/PV MF and were previously treated with ruxolitinib for at least 3 months and with either inadequate efficacy response (defined as < 10% spleen volume reduction [SVR] by MRI/CT or < 30% decrease in spleen size by palpation from baseline) or spleen regrowth to < 10% SVR or < 30% decrease in spleen size from baseline following an initial response were recruited to receive jaktinib 100 mg twice daily. The primary endpoint was the proportion of pts with SVR ≥ 35% from baseline (SVR35) at week (wk) 24, measured by MRI/CT images and assessed by Independent Review Committee. Secondary endpoints included the best spleen response rate (defined as achieving SVR35 at any time), the proportion of pts with ≥ 50% reduction in MPN Symptom Assessment Form Total Symptom Score (MPN-SAF TSS), improvement of anemia and safety. Results: A total of 34 pts were enrolled. The median duration of previous ruxolitinib treatment was 18.6 months (range 3.4-70.1). The median baseline TSS was 19.5 (range 1-55), hemoglobin (Hb) was 101.5 g/L (range 61-149), and platelets was 159×10 9 /L (range 66-951). 11 pts (32.4%) achieved SVR35 at wk 24. The best spleen response rate was 38.2% (13/34). The median time to achieve the first SVR35 was 8.1 weeks, and the median duration of response was not reached. At wk 24, 13 pts (46.4%) achieved a ≥ 50% improvement in TSS from baseline. Of 16 transfusion-independent pts with Hb ≤ 100 g/L at baseline, 8 (50.0%) had a ≥20 g/L Hb increase by wk 24. Of 6 pts who required RBC transfusion at baseline, 2 had a 50% decrease in RBC infusion by wk 24. The median jaktinib exposure time was 231 days (range 96-371). 23 pts (67.6%) had one or more grade ≥3 treatment emergent adverse events (TEAEs). The most common grade ≥3 TEAEs were anemia (32.4%, n = 11), thrombocytopenia (32.4%, n = 11), leukocytosis (20.6%, n = 7) and leukopenia (11.8%, n = 4). Treatment discontinuation due to TEAEs occurred in 2 pts (5.9%). A dose reduction or temporary interruption due to TEAEs were reported in 9 pts (26.5%). Conclusions: MF pts who were refractory/relapsed to ruxolitinib attained substantial spleen response, and reduction in MF-related symptom burden with jaktinib, which could be a new option for MF pts who have failed ruxolitinib. Clinical trial information: NCT04851535 .

Background: For relapsed and refractory multiple myeloma (RRMM), various clinical trials of B-cell maturation antigen-targeted chimeric antigen receptor (CAR) T-cell clinical trials are under way. For one such treatment, CT053, the Phase 1 investigator-initiated CG studies (NCT03380039, NCT03716856, NCT03302403) and the Phase 1 LUMMICAR STUDY 1 (NCT03975907) demonstrated deep and durable responses in heavily pretreated subjects with RRMM. Here we report integrated efficacy and safety of CT053 in Chinese subjects with RRMM based on high-risk factors.

Background: CT053 is a fully human autologous chimeric antigen receptor (CAR) T-cell therapy comprising a B-cell maturation antigen (BCMA)-specific single-chain variable fragment (25C2). A clinical trial of CT053 is ongoing in LUMMICAR STUDY 1 (NCT03975907) for patients with relapsed and refractory multiple myeloma (RRMM) in China. The pivotal Phase 2 of LUMMICAR STUDY 1 is actively enrolling patients. Here, we report clinical data from Phase 1 with 12 months of follow-up.

Abstract Background: Polycythemia vera (PV) is the most common type of Philadelphia-negative myeloproliferative neoplasms (MPNs). PV is a long-term debilitating and life-threatening cancer that is associated with the risk of thrombosis, hemorrhage, and a long-term risk of developing myelofibrosis and acute myeloid leukemia. Early intervention with a disease-modifying treatment that can eradicate the mutated clones is needed to prevent disease progression and transformation. To date, therapeutic options for PV are limited and they only address the signs and symptoms. Most low-risk patients with PV are treated with phlebotomy and low-dose aspirin to manage increased blood viscosity and reduce the risk of vascular events, whereas high-risk and certain low-risk patients are treated with cytoreductive agents. Several cytoreductive agents are available such as hydroxyurea (HU) which is commonly used as a first-line therapy. Ruxolitinib, a JAK2 inhibitor, is also used. While interferon alfa agents have been used off label in clinical practice for more than three decades, their use has been limited due to the tolerability concerns. Ropeginterferon alfa-2b (P1101), a long-acting, mono-pegylated proline interferon, was developed for the treatment of MPNs, including PV. The novel formulation of P1101 improves its pharmacokinetic properties allowing treatment every 2 weeks with improved tolerability and convenience. P1101 was evaluated for the treatment of PV in the phase 3 PROUD-PV trial and its extension study CONTINUATION-PV. In the PROUD-PV study, due to the slow P1101 titration schedule, the maximum P1101 dose was not reached until week 28 and the primary analysis was done at 52 weeks. In CONTINUATION-PV, when patients were on their effective doses, a significantly higher proportion of patients treated with P1101 achieved a complete hematologic response (CHR) with improved disease burden compared to HU-treated patients. At 48 months there was a significant reduction in allelic burden from a baseline of 37.3% to 9.8% with 13.8% of patients achieving a complete molecular response (CMR). The molecular response rates (complete + partial) at 60 months was 69.1%. P1101 was approved by the European Medicines Agency in 2019 and the Taiwan Food and Drug Administration in 2020 as monotherapy in adults for the treatment of PV without symptomatic splenomegaly. Here, we describe a phase 2 study of P1101 in Chinese patients with PV utilizing an accelerated P1101 dose titration schedule. Study Design and Methods: This phase 2, multicenter, single-arm study is designed to evaluate safety and efficacy of P1101 in Chinese patients with PV utilizing a 250-350-500 ug P1101 dose titration schedule. The primary analysis will be conducted at 24 weeks. The study will recruit approximately 49 subjects in 15-20 sites in China. Key eligibility criteria include diagnosis of PV according to the 2016 WHO criteria, and resistance or intolerance to prior HU according to 2020 guidelines of CSCO. Patients who previously received interferon therapy have to be anti-P1101 binding antibody negative during the screening visit to be eligible. The study excludes patients with symptomatic splenomegaly. Eligible patients receive subcutaneous administration of P1101. Patients will receive an initial dose of 250 µg at Week 0, 350 µg at Week 2, and then 500 µg at Week 4. The dose is maintained at the highest dose that can be tolerated and delivers the best disease response. The maximum recommended dose is 500 μg every 2 weeks. Low-dose aspirin is administered during the 52 weeks of study treatment, unless contraindicated. The primary efficacy endpoint is the phlebotomy-free CHR rate at Week 24. Secondary endpoints include changes in hematocrit, white blood cell count, platelet count; time requiring no phlebotomy; time to first response; and duration of response. All patients will continue receiving treatment until week 52 to provide long-term follow-up information (blood parameters, molecular and cytogenetic data, safety parameters, and optional bone marrow data). This study has been granted IND approval by China CDE on Apr2021. Recruitment is expected to begin in early September 2021 with trial results expected in Q3 2022. Figure ： Study Design Figure 1 Figure 1. Disclosures Zagrijtschuk: PharmaEssentia U.S.A. Corp.: Current Employment. Urbanski: PharmaEssentia Corporation: Current Employment. Qin: PharmaEssentia Corp.: Current Employment.

Background: B cell maturation antigen (BCMA) is a potential therapeutic target in multiple myeloma. CT053 comprises autologous T cells transduced with a second-generation chimeric antigen receptor (CAR) utilizing a fully human BCMA-specific single-chain fragment variant (25C2) with high binding affinity. CT053 was firstly studied in a single-arm, open-label Phase I, investigator-initiated program (NCT03716856, NCT03302403, and NCT03380039) in eastern China. Here we present the 24-month follow-up results of the study. Methods: The multicenter exploratory Phase 1 studies included adult subjects with relapsed/ refractory multiple myeloma (RRMM) who had received at least 2 prior lines of myeloma treatment. After preconditioning treatment with fludarabine and cyclophosphamide for 2-4 days, 21 subjects received one cycle of 1.5 × 108 T cells CT053 CAR-BCMA T cells. Three subjects respectively received 0.5 × 108, 1 × 108, or 1.8 × 108 cells. The primary objective was subject safety. The secondary objectives were pharmacokinetics and efficacy. Efficacy was assessed according to IMWG 2016 criteria. Results: A total of 24 subjects with a median age of 60.1 years (range, 38.5-69.9) were enrolled from Sept. 10, 2017 to Sept. 22, 2018. The subjects had a median of 4.5 (range, 2-11) prior lines of therapy, and 41.7% (10/24) underwent autologous stem cell transplantation. At baseline, 10 subjects (41.7%) had concomitant extramedullary involvement, 8 subjects (33.3%) had ECOG scores 2-3, and 9 subjects (37.5%) reported ISS Grade III. As of June 30, 2020, 9 subjects completed 24 months of follow-up with responses including 8 stringent complete response (sCR) and 1 complete response (CR). Also, 15 subjects discontinued prior to completing the 24-month follow-up, of whom 13 discontinued due to disease progression (PD), and 2 discontinued for other anticancer therapy. The overall response rate was 87.5% (21/24) including 79.2% (19/24) with complete responses or stringent complete responses (3 CR, 16 sCR). The median duration of response (DOR) was 21.8 months (95%CI: 9.2, not evaluable [NE]). The median progression-free survival (PFS) was 18.8 months (95%CI: 10.1, NE), with 6-month and 12-month PFS rates of 87% and 60.9%, respectively. Thirteen subjects progressed with median PFS of 10.2 months (range, 0.9-23 months): 3 progressed within 6 months, 6 progressed within 6-12 months, and 4 within 12-24 months. Compared to 9 subjects with persistent CR/sCR, the 13 progressed subjects had a higher percentage of ECOG scores 2-3 (46.2% vs 22.2%), ISS Grade III (53.9% vs 11.1%) and high-risk cytogenetics profiles (53.8% vs 33.3%). Rates of concomitant extramedullary diseases were similar, 46.2% and 44.4%, respectively. Hematological toxicities were the most common treatment-related adverse events of grade (G) 3 or higher, including leukopenia (83.3%), neutropenia (85%), lymphocytopenia (79.2%) and thrombocytopenia (20.8%). In general, cytokine release syndrome (CRS) occurred at 1-4 days and resolved in a median 6 days (range, 3-9 days). Low-grade CRS was reported in 15 of 24 (62.5%) subjects. All CRS events (4 G1, 11 G2) resolved within 2-8 days; among them, 9 patients received a low dose of tocilizumab 4-6 mg/kg. One patient experienced G3 neurotoxicity, presenting as epilepsy and accompanied by simultaneous G2 CRS. This patient fully recovered within 3 days after treatment with methylprednisolone, diazepam and sodium valproate. Six patients (25%) experienced 10 cases of treatment-related serious adverse events (SAEs), including lung infection (3), gastroenteritis (1), neutropenic infection (1), fever (1) and hematological toxicities (4). By the cutoff date, one subject died of SAE a (bone morrow failure and neutropenic infection) and PD, and seven subjects died of PD. CAR-BCMA T cell expansion was detectable as early as day 1-7 after infusion and reached peak values on day 7-21 with the highest concentration at 4.5×105 copies/µg genomic DNA. Median T cell persistence was 172 days. The longest persistence of CAR-BCMA copies was measured at 341 days and continues. No immunogenicity was detected. Conclusion: These studies demonstrated that CT053 had excellent efficacy in RRMM, showing early, deep and durable response with 21.8 months DOR. CT053 was well tolerated among the subjects. Figure Disclosures Li: CARsgen Therapeutics Co. LtD: Current Employment, Current equity holder in private company. Wang:CARsgen Therapeutics Corp.: Current Employment. Xiao:CARsgen Therapeutics Corp.: Current Employment. Yuan:CARsgen Therapeutics Corp.: Current Employment. Ma:CARsgen Therapeutics Corp.: Current Employment.

Background: B cell maturation antigen (BCMA) is a potential therapeutic target in multiple myeloma. CT053 CAR-BCMA, which is a BCMA-specific chimeric antigen receptor (CAR) T cell, consists of autologous T cells genetically modified with a second-generation CAR incorporating a fully human anti-BCMA single chain fragment variant, a 4-1BB co-stimulatory domain and a CD3-zeta signaling domain. CT053 was studied in a single-arm, open-label phase I program (NCT03716856, NCT03302403, and NCT03380039) in eastern China. Methods: This investigation is a 3-site study in adult subjects with relapsed/refractory multiple myeloma (rrMM) who had received at least 2 prior myeloma regimens. Subjects received one cycle of CT053 CAR-BCMA after fludarabine/cyclophosphamide infusion. The primary objective was the assessment of subject safety. The secondary objectives were pharmacokinetics and efficacy. Efficacy was assessed according to IMWG 2016 criteria. The data cutoff date was June 30, 2019. Results: A total of 24 subjects with median age of 60.1 years (range, 38.5-69.9) were enrolled from Sep 10, 2017 to Sep 22, 2018 (Table 1). The subjects had a median of 4.5 (range, 2-11) prior regimens of therapy, and 41.7% (10/24) underwent autologous stem cell transplantation. At baseline, eleven out of 24 subjects (45.8%) had concomitant extramedullary involvement. Eight subjects (33.3%) had ECOG score 2-3, and 9 subjects (37.5%) reported ISS grade III. All subjects received lymphodepletion preconditioning of fludarabine/cyclophosphamide for 2-4 days, followed by one cycle of CT053 at a dose of 1.5 x 108 T cells except 3 subjects who received 0.5 x 108, 1 x 108, and 1.8 x 108 cells, respectively. The overall response rate was 87.5% (21/24) including 79.2% (19/24) with complete responses or stringent complete response (5 CR, 14 sCR). As shown in Figure 1, P1 who received the lowest dose of 0.5 x 108 experienced partial response (PR) at M1 and very good partial response (VGPR) at M2. P1 then converted to CR at M14 and sCR at M16. Among 20 subjects who underwent the evaluation of minimal residual disease (MRD) status, 17 achieved MRD-negative (≤10−4 nucleated cells) and reported a tumor response (17 CR/sCR). In 13 subjects with ongoing CR/sCR, the median follow-up after CT053 infusion was 383 days (range, 301-467). Nine subjects progressed with median progression-free period of 281 days (range, 57-573); among them, 5 progressed within 6-12 months, 1 at 13 months and 1 at 19 months. Compared to 13 subjects with persistent CR/sCR, the 9 progressed subjects were observed to have a higher percentage of ECOG score 2-3 (66.7% vs 15.4%), ISS Grade III (55.6% vs 15.4%), and concomitant extramedullary diseases (66.7% vs 38.5%) and a decreased hemoglobin (70g/L vs 92g/L) at baseline. Three subjects died of disease progression at the time of analysis. Hematologic toxic effects were the most common treatment-related adverse events of grade (G) 3 or higher, including white blood cell count decreased (87.5%), neutrophil count decreased (66.7%), lymphocyte count decreased (79.2%) and thrombocytopenia (25%). No dose limiting toxicities were observed. Low-grade cytokine release syndrome (CRS) was reported in 15 of 24 (62.5%) subjects. All CRS events (3 G1, 12 G2) recovered within 2-8 days; among them 8 received tocilizumab. Three subjects (12.5%) had neurotoxicity (2 G1, 1 reversible G3). One subject died of bone marrow failure and neutropenic infection. CAR-BCMA T cell expansion was detected as early as Day 1-7 after infusion and reached peak values on Day 7-21 with the highest at 4.5×105 copies/µg genomic DNA. Median T cell persistence was 172 days. The longest persistence of CAR-BCMA copies was measured at 341 days and continues. Conclusion: This study demonstrated that CT053 had an excellent efficacy and a good safety profile in subjects with rrMM. Disclosures Li: CARsgen Therapeutics Co. Ltd: Employment, Equity Ownership. Xiao:CARsgen Therapeutics Co. Ltd: Employment. WANG:CARsgen Therapeutics Co. Ltd: Employment. Yuan:CARsgen Therapeutics Co. Ltd: Employment. Ma:CARsgen Therapeutics Co. Ltd: Employment.

B-cell maturation antigen (BCMA)-specific chimeric antigen receptor (CAR) T cells (CT053) are autologous T cells genetically modified with a second-generation CAR incorporating a fully human anti-BCMA single chain fragment variant, a 4-1BB co-stimulatory domain and a CD3-zeta signaling domain. CT053 was studied in a single-arm, open-label, 3-site phase I study (NCT03716856, NCT03302403, and NCT03380039).

Introduction: B Cell Mature Antigen (BCMA)-targeted chimeric antigen receptor T (CAR-T) cell therapy emerges as promising treatment for patients with relapse/refractory multiple myeloma (RRMM). Previous studies indicate patients who receive high-dose CAR-T cells may achieve better remission but have worse adverse events, like cytokine release syndrome (CRS). To solve this dilemma, we have developed novel autologous CAR-T therapeutics CT053 that are genetically modified T cells comprising an extracellular anti-BCMA human scFv and an intracellular 4-1BB costimulatory motif connected to a CD3-zeta T cell activation domain. Methods: A multi-center investigator-initiated clinical study is designed to evaluate CT053 in patients with RRMM who have failed in the prior treatment with ≥2 regimens, including a proteasome inhibitor, an immunomodulatory agent, and anti-CD38 monoclonal antibody. All patients have ≥50% BCMA expression on malignant cells. Patients are subjected to the lymphodepletion with 20-25 mg/m2 fludarabine and 300-500 mg/m2 cyclophosphamide daily for 2-4 days prior to receiving single-dose infusion of CT053 CAR-T cells. In case of progressive disease, patient may be dosed again on basis of investigators' evaluation of the disease status, BCMA expression and CAR-T persistence. Most enrolled patients received a single dose of 1.5 x 108 cells, except for 1 patient who received 0.5 x 108 cells and 1 patient who was infused with 1.8 x 108 cells. The primary outcome measure is incidence of adverse events (AEs), including dose-limiting toxicities (DLTs) and CAR T related AEs. Additional outcome measures include clinical response assessed according to the IMWG Uniform Response Criteria for Multiple Myeloma, overall and progression-free survival, pharmacokinetics and pharmacodynamic of CT053. Results: The study was performed in compliance with the declaration of Helsinki. As of the data cut-off date (July 10th, 2018), 16 patients (median 55 [39 to 67] years old) with a median of 3.9 (0.4 to 16.7) years since MM diagnosis, were infused with CT053. Patients had a median of 4 prior different regimens (range 2 to 10), and 56% (9/16) patients received prior autologous or allogeneic stem cell transplant. Among 16 patients, no neurotoxicity and no dose-limiting toxicities (DLT) were observed. The most common grade≥3 CAR-T related AEs were 3 thrombocytopenia (19%), 3 leukopenia (19%), 2 anemia (13%), 2 neutropenia (13%), 2 fever (13%) (Figure 1A). CRS was reported in 3 patients, including 1 Grade 3, 1 Grade 2 and 1 Grade 1, who had rapid recovery after Tocilizumab administration. 13/16 patients were eligible for initial evaluation of early clinical response with a median observation period of 8 (4 to 36) weeks. Overall response rate (ORR) in 13/13 patients was 100% post treatment. 12/13 patients (92%) quickly achieved partial response (4 PR), very good PR (6 VGPR), and complete response (2 CR) within 4 weeks post single-dose infusion (Figure 1B). 5/12 patients (42%) who were dosed at ≥1.5 x 108 CT053 CAR-T cells obtained CR at a median of 8 weeks post treatment. Durable responses from 4 weeks towards the data cut-off date were found in 12/13 patients (92%). One relapse from VGPR by the Week 12 was reported in a patient who had aggressive RRMM at enrollment and received the reduced dose of lymphodepletion regimen at 19 mg/m2 fludarabine and 192 mg/m2 cyclophosphamide for 2 days prior to CT053 infusion. Because positive BCMA expression on malignant cells was verified at relapse, the patient was re-dosed with CT053 at the Week 16 and subjected to the further evaluation. All patients had detectable CAR-T expansion from Day 3 post CT053 infusion. Expansion peaks were found on Day 7 (5/13), Day 14 (6/13) and Day 21 (2/13). 11/13 patients had notable persistence of CT053 CAR-T cells up to 4-6 months. The only relapsed patient had the lowest CAR-T expansion peak among 13 patients, indicating the potential correlation between CAR-T expansion and response outcome. Conclusions: Data from this early-stage clinical study showed the unparalleled safety and efficacy of CT053 CAR-T cells. Major AEs were transient, manageable, and reversible. 100% ORR in 13/13 evaluable patients were reported post single-dose infusion of 0.5~1.8 x 108 cells. 5/12 patients who were dosed at ≥1.5 x 108 CAR-T cells rapidly achieved durable CR at median of 8 weeks, suggesting CT053 could be developed as competitive therapeutics to treat patients with RRMM. Ruan: CARsgen Therapeutics: Employment. Xiao:CARsgen Therapeutics: Employment, Equity Ownership. Wang:CARsgen Therapeutics: Employment, Equity Ownership. Li:CARsgen Therapeutics: Employment, Equity Ownership.