Durable Responses Research Articles

DeLLphi-301: Tarlatamab phase 2 trial in small cell lung cancer (SCLC)—Efficacy and safety analyzed by presence of brain metastasis.

8015 Background: Brain metastases affect 40%–70% of patients with SCLC. Tarlatamab, a BiTE (bispecific T-cell engager) immunotherapy targeting delta-like ligand 3, demonstrated durable responses and promising survival outcomes in patients with previously treated SCLC (10 mg Q2W) (DeLLphi-301; NCT05060016; Ahn M-J, N Engl J Med 2023). Here, tarlatamab efficacy and safety in patients with baseline brain metastases from DeLLphi-301 are reported. Methods: The DeLLphi-301 study design has been published. Patients with treated, stable, asymptomatic brain metastases were included. Subgroup analyses for efficacy (blinded independent central review [BICR] assessments) and safety by presence or absence of baseline brain metastases were performed. Intracranial activity was assessed. Post enrollment, brain imaging was performed if clinically indicated. Results: As of 27 June 2023, 186 patients had received tarlatamab (ECOG PS: 0–1; median prior lines of therapy: 2; median follow-up: 13.6 months). 29% of patients (54/186) had treated and stable brain metastases at baseline. Most patients (91%) with brain metastases had received prior local radiotherapy; 6% each had received surgery only or both radiotherapy and surgery. Overall systemic objective response rate (ORR; RECIST 1.1) was 45.3% in patients with brain metastases and 32.6% in patients without brain metastases (Table). Any grade immune effector cell associated neurotoxicity syndrome and associated neurological events occurred in 24.1% of patients with brain metastases and in 13.6% of patients without brain metastases; grade ≥ 3 events occurred in the 100 mg group only: 9.4% and 1.8%, respectively, and did not lead to tarlatamab discontinuation in any patient with brain metastases. Analysis of intracranial activity will be presented. Conclusions: Tarlatamab showed promising efficacy and a favorable benefit-risk profile in patients with previously treated SCLC and stable brain metastases. Clinical trial information: NCT05060016 . [Table: see text]

Outcomes following long-term response to immune checkpoint inhibitors in patients with advanced melanoma.

9520 Background: Immune checkpoint inhibitors (ICI) targeting PD-1 and CTLA-4 can achieve durable responses. Historically, therapies in advanced malignancies were considered palliative, however long-term results from ICI melanoma studies suggest cure may be possible for some patients (pts). Despite clinical trial data, little is known about the risk, character, and clinical outcome of late recurrences after ICI. Methods: ICI treated pts with advanced melanoma who had a long-term disease control, defined as not requiring a subsequent line of systemic therapy within 3 years, were retrospectively identified at 11 centres. Those who had progressive disease managed with local therapies were included if no new systemic therapy was commenced within the 3 years. Demographics, disease characteristics, treatment, toxicity, recurrence patterns, management and outcomes were collected. Results: 567 pts were identified, with a median follow up of 7 years since start of therapy. At ICI commencement, 41% and 17% had M1c or M1d disease respectively, 26% had an elevated LDH, 33% were BRAF mutant and 24% had received prior therapy. The ICIs received were anti-PD-1 +/- an investigational agent (59.3%), anti-PD-1 plus anti-CTLA-4 (35.8%), or an anti-CTLA-4 (5%). The median duration of therapy was 18 months, with 31% of pts stopping due to toxicity. 63 pts (11.1%) had oligo-progression within 3 years from ICI start. 53 pts (9.3%) had progression after 3 years, with median time to progression of 16.3 months. Subsequent late progression was more common in those who had oligo-progression within 3 years of treatment compared to those who had not (14/63, 22% vs 39/504, 7.7%, P<0.001). The risk of late progression was lower in those who achieved a complete response (CR) compared to those without a CR (23/369, 6.2% vs 30/198, 15.2%, P<0.001). The landmark 5 year PFS was 95% compared to 89% in those with or without a CR respectively. Duration of therapy, treatment cessation due to toxicity, or corticosteroid use were not associated with the risk of late progression. Most late progression occurred within year 3 to 5 (38/53, 72%). 15 pts who progressed after 3 years were managed with local therapy alone. In progressors retreated with PD-1 alone as the next subsequent therapy, 14 of 26 (54%) responded (7 CR, 7 PR). In the total cohort, there were 31 (5.5%) deaths, 7 (1.2%) from melanoma. Of the pts with a CR, 14 (3.7%) died, only 1 (0.3%) from melanoma. Of the 53 pts who progressed after 3 years, 10 (19%) died, 7 (13%) from melanoma. Conclusions: In this population of pts with advanced melanoma with long term disease control from ICI, the risk of subsequent disease progression and death was low (1.2%). Predictors for late progression after 3 years were a non-CR best response and prior progression within 3 years. This and other data suggest a significant proportion of long-term ICI responders are likely cured, and may inform frequency and duration of follow up.

Temozolomide and nivolumab in patients with refractory metastatic melanoma (MM).

e21521 Background: Immune checkpoint inhibitors (ICI) are the standard treatment for patients (pts) with MM. However, only a subset of pts respond to ICIs. Temozolomide (TEM) is used in refractory settings but with low objective response rates and no clear overall survival benefit. The efficacy of combined ICI + TEM is not well described. Methods: This was a single center, retrospective study of pts with MM who received treatment with nivolumab (NIVO) and TEM or TEM alone between 11/6/2013 and 11/6/2023. Demographic information, disease characteristics, LDH, treatment, toxicity, objective response, and outcomes were collected. Results: 34 patients were included. 16 were treated with NIVO + TEM and 18 were treated with TEM alone. In the NIVO + TEM group, 81% were male (n = 13) with median age of 59.5 years (range 20-79), and in the TEM group, 56% were male with median age 61 (range 35-81). For NIVO + TEM, 31% had partial response (PR; n = 5), 6% had stable disease (SD, n = 1), and 63% had progressive disease (PD; n = 10). For TEM, 11% had PR (n = 2), 22% had SD (n = 4), and 67% had PD (n = 12) (p = 0.37). For NIVO + TEM, 2 PRs were durable, ongoing at 442 and 741 days; 3 PRs were transient (85-179 days); 1 pt had durable SD ongoing at 201 days. For TEM, PR durations were 173 and 504 days, and SD durations between 213-435 days. Five pts with PD treated with NIVO + TEM had mixed responses (31%) compared with 1 pt treated with TEM (6%). Median progression free survival (PFS) was 80 days (range 11-748) for NIVO + TEM and 55.5 days (7-415) for TEM (p = 0.31). Median overall survival (OS) was 160 days (43-363) for NIVO + TEM and 118 days (7-1938) for TEM (p = 0.15). There were 26 adverse events (AEs) for NIVO + TEM (27% grade 1, 42% grade 2, 19% grade 3, and 12% grade 4; thrombocytopenia and pneumonitis), and 25 AEs for TEM (40% grade 1, 40% grade 2, 12% grade 3, and 8% grade 4; thrombocytopenia) [p = 0.64]. Conclusions: NIVO + TEM occasionally produced durable responses, although outcome metrics were not clearly superior to TEM alone in this small study. Further studies should quantify the benefit of ICI + chemotherapy regimens in refractory MM. [Table: see text]

Pooled analysis by best confirmed response to trastuzumab deruxtecan (T-DXd) in patients (pts) with HER2+ metastatic breast cancer (mBC) from DESTINY-Breast-01, -02, and -03.

1023 Background: DESTINY-Breast (DB)-01, -02, and -03 evaluated T-DXd in pts with HER2+ mBC who received ≥1 prior line of therapy. These studies showed confirmed objective response rates by independent central review (ICR; blinded for DB-02 and -03) of 62%, 70%, and 79% and complete response (CR) rates of 7%, 14%, and 21%, respectively, with T-DXd. We report a pooled analysis according to pts’ best confirmed response in DB-01, -02, or -03. Methods: Endpoints included best confirmed response per (blinded) ICR ([B]ICR) based on RECIST v1.1, duration of response (DoR), progression-free survival (PFS) by (B)ICR, overall survival (OS), and safety. Results: The median (range) duration of T-DXd treatment for pts with a CR, partial response (PR), or stable disease (SD)/progressive disease (PD) was 27.4 (4.5-45.1) mo, 14.0 (2.1-39.3) mo, or 6.2 (0.7-40.1) mo, respectively. Of 834 evaluable pts assigned to T-DXd in DB-01, -02, or -03, 125 (15.0%) had a CR, 477 (57.2%) had a PR, and 232 (27.8%) had SD/PD. Pts with CR had a median of 2 prior regimens (range, 1-11) in the metastatic setting, whereas pts with PR or SD/PD had a median of 3 prior regimens. As shown in the Table, pts with CR had more favorable PFS and OS outcomes vs pts with PR or SD/PD. The proportion of pts with drug-related, serious treatment-emergent adverse events (TEAEs) was numerically lower in pts with CR (8.0%) than those with PR (12.4%) or SD/PD (15.5%). Pts with CR also had numerically lower rates of drug-related TEAEs associated with T-DXd discontinuation (14.4% vs 17.8% or 16.8%) and adjudicated drug-related interstitial lung disease (ILD)/pneumonitis (8.8% [0 fatal] vs 15.1% [2 fatal] or 11.6% [5 fatal]) and longer median time to first ILD onset (461 days vs 211 or 125 days) vs pts with PR or SD/PD. Conclusions: Pts treated with T-DXd benefited from durable responses resulting in prolonged PFS and OS, especially those with a CR. Despite longer treatment duration in responders, safety remained generally manageable and did not result in a higher percentage of pts with TEAEs over time. These results further support the use of T-DXd across broad pt groups with HER2+ mBC. Clinical trial information: NCT03248492 , NCT03523585 , NCT03529110 . [Table: see text]

TRICK-MCC: A proof-of-concept, investigator-initiated study of combination therapy with anti–PD-1, anti–LAG-3, and anti–TIM-3 in participants with advanced or metastatic PD-(L)1 refractory Merkel cell carcinoma.

TPS9618 Background: Merkel cell carcinoma (MCC) is an aggressive and highly immunogenic skin cancer often associated with the Merkel cell polyomavirus (MCPyV). Immune checkpoint inhibition (ICI) via PD-(L)1 blockade can promote durable responses among patients with metastatic MCC, yet >50% of MCC patients experience disease progression. There is an unmet need for effective treatment options for these patients. One possible strategy to overcome primary and secondary resistance in PD-(L)1 refractory MCC is concurrent targeting of multiple immune checkpoints to facilitate reversal of chronic T cell exhaustion. Based on our preliminary data revealing high expression of PD-1, LAG-3 and TIM-3 on MCC-specific CD8 T cells, which appear to increase upon clinical disease progression in the context of treatment with PD-(L)1 blockade, we hypothesize that concurrent blockade of PD-1, LAG-3 and TIM-3 will overcome immune evasion in patients with PD-(L) refractory MCC. Methods: TRICK-MCC (Triple Immune Checkpoint Inhibition in MCC) is an investigator initiated, Phase 2 clinical trial investigating concurrent treatment with anti-PD-1 (retifanlimab), anti-LAG3 (INCAGN02385) and anti-TIM-3 (INCAGN02390) in patients with advanced/metastatic MCC that has progressed after treatment with anti-PD-(L)1. Target enrollment is 20 patients total, with 5 patients enrolled as of Jan 2024. Patients will receive anti-PD-1 q4w and anti-TIM-3 and LAG-3 q2w for up to 24 weeks (Induction Phase) followed by all drugs q6w (Maintenance Phase). Treatment will end 2 years after starting the study drugs, or upon disease progression, unacceptable toxicity, or study withdrawal. Primary objective is objective response rate (ORR). Secondary objectives are duration of response, progression free survival, overall survival, and incidence and severity of adverse events. Interim analysis will be done after 10 patients have been enrolled and followed sufficiently long to assess ORR. An observed ORR of 25%will be considered as clinically meaningful in this population with no reliable standard treatments. Serial tumor biopsies and blood samples will be obtained in all patients, unless deemed unsafe or not feasible. Planned correlative studies aim to better characterize the prevalence and significance of cancer-specific T cell exhaustion (through rigorous study of MCPyV-specific T cells), the immunologic effects of triple ICI, and alternative mechanisms of PD-(L)1 resistance beyond T cell exhaustion in PD-(L)1 resistant tumors. We hope to gain insights that are broadly applicable to solid tumor immunotherapy. Clinical trial information: NCT06056895 .

Using serial 18F-FDG PET/CT PERCIST response to predict responses to immune check point inhibitors in patients with advanced cutaneous squamous cell carcinoma.

9548 Background: The role of serial 18F-FDG-PET/CT imaging in predicting long term efficacy of PD-1 targeted immune checkpoint inhibitor (ICI) in advanced cutaneous squamous cell carcinoma (cSCC) is unknown. This study aims to correlate PET PERCIST response with time to progressive disease. Methods: This was a single-centre retrospective study of patients treated with ICI for advanced cSCC who had baseline and serial FDG-PET/CT within 4-months of commencement of ICI. PERCST 1.0 was calculated by two radiologists independently and classified into complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), and progressive metabolic disease (PMD). The primary endpoint was time to progression from commencement of ICI. Progression was determined by a multidisciplinary team combining clinical and radiological assessments. Results: Of the 242 patients treated with ICI for advanced cSCC during 2018-2023, 83 (34%) patients had a serial FDG PET. Of these, 53 patients met the inclusion criteria of ≤4-months from ICI to second PET. CMR (54.7%), PMR (15.1%), SMD (11.3%) and PMD (18.9%) were seen as initial responses by PERCST 1.0. With a median follow-up of 8-months (1-55), progressive disease as determined by the multidisciplinary team was observed in 11 patients (21%). For these 11 patients, the 4-month PERCST 1.0 response was measured as CMR (n=1), PMR (N=1), SMD (N=2) and PMD (N=7). The median TTP was significantly higher in CMR/ PMR vs SMD/PMD (55 vs 4-Months, P<0.001). At data cut off, 94.6% (N=35) of patients with a 4-month PET PERCST 1.0 CMR/ PMR assessment did not progress clinically. Clinical response was maintained at a minimum of 12-months in 94.7% (n=18) of those responding. Conclusions: Rate of CMR and PMR in advanced cSCC is high with ICI. Early PET CMR/ PMR appears to predict long term durable responses. Incorporation of PET/CT into the assessment of response in cSCC may help guide treatment decisions by early identification of those patients not responding to ICI.

Olutasidenib for mutated IDH1 acute myeloid leukemia: Final five-year results from the phase 2 pivotal cohort.

6528 Background: Olutasidenib is a potent, selective, oral inhibitor of mIDH1 and is FDA-approved for relapsed/refractory (R/R) acute myeloid leukemia (AML) based on a registrational, Phase 2, open-label, multicenter trial (NCT02719574). We report final five-year results from the pivotal cohort. Methods: In the pivotal cohort of the Phase 2 trial, patients with mIDH1 AML received olutasidenib 150mg BID. Primary endpoint was complete remission (CR) + CR with partial hematologic recovery (CRh) by modified IWG Criteria 2003. Data cutoff: May 15, 2023. Results: Baseline characteristics of 153 enrolled patients are shown in Table. Of 147 efficacy evaluable patients, CR was achieved in 32% (95% CI: 24.5, 40.2) and CR/CRh in 35% (95% CI: 27, 43; P<0.0001). Median time to CR/CRh was 1.9 mo (range: 0.9, 5.6). The median duration of CR/CRh was 25.3 mo (95% CI: 13.5, not reached), with maximum duration 54.6 mo. Overall response rate was 48% (95% CI: 40, 56.7), with median duration 15.5 mo (95% CI: 7.4, 26.2) and maximum duration 54.6 mo. Median overall survival was 11.6 mo (95%CI: 8.9, 15.5). In the 12 patients R/R to prior venetoclax, 33% achieved a CR/CRh; median duration of CR/CRh is not reached (ongoing at 54.3 months), and median overall survival is 16.2 months (95%CI: 2.6, not reached). Transfusion independence from red blood cells and platelets was achieved in 34 of 87 (39%) patients and 28 of 69 (41%) patients, respectively, who were dependent at baseline. 16 (11%) patients proceeded to stem cell transplant. The 5-year safety profile was consistent with what was previously reported. The most common AEs (% reported over 3 years and over the full 5 years) were: febrile neutropenia (22% and 22%), constipation (26% and 27%), diarrhea (20% and 21%), nausea (38% and 39%), fatigue (23% and 23%), pyrexia (24% and 24%), hypokalaemia (20% and 22%), red blood cell count decreased (26% and 26%), white blood cell count increased (25% and 25%). Differentiation syndrome was reported in 14% by Year 3, with no new events by Year 5. The safety profile was stable with long-term follow up. Conclusions: This analysis provides an additional 2 years of data beyond the results that led to FDA approval of olutasidenib. This first report of the five-year data further demonstrates the rapid and durable responses observed with olutasidenib in heavily pretreated patients with mIDH1 AML, including those R/R to prior venetoclax. Clinical trial information: NCT02719574 . [Table: see text]

Pembrolizumab (pembro) for locally advanced (LA) or recurrent/metastatic (R/M) cutaneous squamous cell carcinoma (cSCC): Long-term results of the phase 2 KEYNOTE-629 study.

9554 Background: Pembro monotherapy is approved in certain countries, including the US, for treatment of LA or R/M cSCC based on results from the open-label phase 2 KEYNOTE-629 trial (NCT03284424). Promising antitumor activity was demonstrated with pembro in both the LA and R/M cohorts. ORR (95% CI) was 50.0% (36.1-63.9; 16.7% CRs) in the LA cohort and 35.2% (26.2-45.2; 10.5% CRs) in the R/M cohort. We present data from KEYNOTE-629 with an additional follow-up of 38 mo for LA and R/M cohorts. Methods: Adults with histologically confirmed LA or R/M cSCC, measurable disease per RECIST v1.1 by blinded independent central review (BICR), and ECOG PS 0 or 1 received pembro 200 mg IV every 3 weeks for up to 35 cycles (~2 years). The primary end point was ORR per RECIST v1.1 by BICR. Secondary end points were DOR, DCR (CR + PR + SD ≥12 wks), and PFS per RECIST v1.1 by BICR; OS; and safety. End points were analyzed in pts who received ≥1 dose of pembro. Results: A total of 159 pts were treated with pembro (LA, n = 54; R/M, n = 105). As of September 13, 2023, 33 pts (20.8%) completed treatment and 126 pts (79.2%) discontinued treatment. Median (range) follow-up was 52.4 mo (47.6-56.9) for the LA cohort, 64.7 mo (62.1-69.5) for the R/M cohort, and 63.1 mo (47.6-69.5) in the total population. ORR and DCR are shown in the table. Median DOR (range) was 47.2 mo (1.0+ to 49.9+) in the LA cohort, not reached (NR; 2.7 to 64.2+ mo) in the R/M cohort, and 52.5 mo (1.0+ to 64.2+) in the total population; the proportion of responders with responses ≥12 mo by Kaplan-Meier estimate were 84.8%, 77.8%, and 80.7%, respectively. Median (95% CI) PFS was 14.4 mo (5.5-43.6) in the LA cohort, 5.7 mo (3.1-8.5) in the R/M cohort, and 8.0 mo (5.3-14.4) in the total population; 12-mo rates were 56.7%, 37.3%, and 43.7%, respectively. Median (95% CI) OS was NR (33.3-NR) in the LA cohort, 23.8 mo (13.4-30.9) in the R/M cohort, and 29.8 mo (20.0-42.8) in the total population; 36-mo rates were 62.0%, 39.5%, and 47.0%, respectively. Grade 3-5 treatment-related AEs occurred in 11.3% of pts, and grade 3-5 immune-mediated AEs and infusion reactions occurred in 8.8% of pts. Two pts (1.3%) died due to a treatment-related AE (colitis, cranial nerve disorder). Conclusions: With a median follow-up of more than 5 years, pembro continued to show durable responses in pts with LA or R/M cSCC. No new safety signals were observed. Results from this study continue to support the use of pembro in this pt population. Clinical trial information: NCT03284424 . [Table: see text]

Pembrolizumab (pembro) in patients (pts) with sorafenib-treated (cohort 1) and treatment (tx)-naive (cohort 2) advanced hepatocellular carcinoma (aHCC) after additional follow-up in the phase 2 KEYNOTE-224 study.

4100 Background: Based on the results of the open-label, phase 2 KEYNOTE-224 study (NCT02702414), pembro received US FDA and the Center for Drug Evaluation of the China National Medical Products Administration approval for pts with sorafenib-treated aHCC (cohort 1). Durable activity and manageable safety were also observed for pts with tx-naive aHCC in cohort 2 of KEYNOTE-224. We report updated efficacy and safety from both cohorts of KEYNOTE-224 after approximately 7 and 5 years of median follow-up, respectively. Methods: Adults with pathology-confirmed aHCC whose disease progressed after or who were intolerant to sorafenib tx (cohort 1) and adults with histologically, cytologically, or radiologically confirmed aHCC with no prior systemic tx (cohort 2) were eligible. Pts in both cohorts had BCLC stage C or B not amenable or refractory to locoregional therapy and not amenable to curative tx, Child-Pugh A liver function, measurable disease per RECIST v1.1, and ECOG PS 0 or 1. Pts received pembro 200 mg IV Q3W for ≤35 cycles (~2 y). Primary end point was ORR per RECIST v1.1 by BICR. Secondary end points included DOR, DCR, TTP, and PFS (all per RECIST v1.1 by BICR), OS, and safety/tolerability. Results: A total of 155 pts enrolled in cohorts 1 (n = 104) and 2 (n = 51) received ≥1 dose of pembro. Median follow-up, defined as time from first dose to data cutoff (Sept 29, 2023), was 83.0 mo (range, 79.3-87.3) for cohort 1 and 58.8 mo (range, 55.3-60.8) for cohort 2. In each cohort, 90% of pts discontinued, mostly due to progressive disease (59%); 10% of pts in each cohort completed 2 y of tx. ORR was 18.3% (95% CI, 11.4-27.1) for cohort 1 (5 CRs [4.8%] and 14 PRs [13.5%]) and 17.6% (95% CI, 8.4-30.9) for cohort 2 (2 CRs [3.9%] and 7 PRs [13.7%]). Median DOR was 21.0 mo (range, 3.1 to 75.8+) for cohort 1 and 24.7 mo (range, 3.1 to 53.4+) for cohort 2; 77%/43% and 76%/64% of responders, respectively, had a response duration of ≥12 mo/≥24 mo per the Kaplan-Meier method for censored data. Data for PFS, TTP, and OS are shown in the Table. Tx-related AEs were reported in 76 pts (73.1%; grade 3-5, 27 [26.0%]) in cohort 1 and 28 pts (54.9%; grade 3-5, 8 [15.7%]) in cohort 2. Conclusions: Pembro continued to provide durable responses in pts with aHCC with or without prior systemic therapy, with some lasting beyond 20 mo; long-term effects on OS beyond 24 mo and manageable safety were also observed. Together with data from KEYNOTE-394 and KEYNOTE-240, these data support the efficacy and safety of pembro as a tx option for aHCC. Clinical trial information: NCT02702414 . [Table: see text]

ATHENA: A phase 1/2 study of AZD5851, a chimeric antigen receptor (CAR) T-cell therapy directed against GPC3 in adult patients with advanced/recurrent hepatocellular carcinoma (HCC).

TPS2675 Background: Checkpoint inhibitor therapy is the standard first-line treatment for advanced/recurrent HCC, but there is a significant unmet therapeutic need for patients (pts) who progress after first-line treatment. Adoptive cellular immunotherapy may provide a novel treatment option. Glypican-3 (GPC3), a heparan sulfate proteoglycan, is overexpressed by tumor cells in HCC and virtually absent in healthy tissues, making it an ideal target for CAR-T therapy. AZD5851 is an autologous CAR-T product that expresses a CAR specific for GPC3 and a dominant negative (dn)TGFβRII as an armoring strategy. Expression of dnTGFβRII can block TGFβ signaling, protecting CAR T-cells from the immunosuppressive effects of this cytokine. Early clinical data with C-CAR031, a CAR-T product with the same GPC3-specific CAR and dnTGFβRII-armoring transgene as AZD5851, showed promising tolerability and antitumor activity in pts with HCC [1]. ATHENA (NCT06084884) is a first-in-human, single-arm, open-label, multicenter phase 1/2 study to evaluate the safety, tolerability, and antitumor activity of AZD5851 in pts with GPC3+ advanced/recurrent HCC, for whom ≥1 prior line of standard therapy failed or was not tolerable. Methods: Eligible pts are aged ≥18 years with histologically confirmed advanced/recurrent or metastatic and/or unresectable HCC, GPC3+ tumor sample as determined by immunohistochemistry, ≥1 prior line of standard systemic therapy, ≥1 measurable lesion per RECIST 1.1, Child-Pugh A, ECOG PS 0/1, and adequate organ and bone marrow function. Approximately 24 pts will be enrolled in Part A (Phase I, dose escalation) and 50 in Part B (Phase II dose expansion). Pts will undergo apheresis to collect peripheral blood mononuclear cells for AZD5851 production, after which they may receive approved bridging therapy for disease control. Upon successful generation of AZD5851 product, pts will undergo lymphodepletion before receiving a single dose of IV AZD5851. Subsequent follow-up is divided into 3 stages: Stage 1, active follow-up of all pts through 6 months post AZD5851 infusion; Stage 2, further evaluation of pts who have not progressed or started a new anticancer regimen during Stage 1; Stage 3, long-term follow-up for all pts who have received AZD5851. The primary endpoints are to assess the safety/tolerability of AZD5851 (both study parts), and to determine the recommended dose(s) of AZD5851 for expansion and phase 2 trials (Part A). Secondary endpoints include efficacy (objective response rate, best overall response, duration of response, disease control rate, durable response rate, time to response, progression-free survival, and overall survival) and pharmacokinetics. Exploratory endpoints include pharmacodynamic biomarkers and immunogenicity. Enrollment began Nov 2023. 1. Zhang et al. AACR 2023. Abstract CT097. Clinical trial information: NCT06084884 .

Treatment-free survival after immunotherapy discontinuation in advanced melanoma: A systematic review and meta-analysis of real-world studies.

e21523 Background: Immune checkpoint inhibitors (ICIs) have altered the treatment landscape of advanced melanoma with remarkable improvements in progression-free survival (PFS). Durable responses to ICI cessation have been shown in early clinical trials for ICI usage in melanoma, although the optimal duration of immunotherapy remains unclear. Treatment-free survival (TFS) after immunotherapy cessation for patients with complete response (CR), partial response (PR), and stable disease (SD) has been reported in real-world studies and may help to guide discontinuation of ICI therapy. Methods: A systematic search was conducted using PubMed, Embase, and the Cochrane Library to identify real-world studies reporting TFS after immunotherapy in advanced cutaneous melanoma patients with CR, PR, and SD at 12 and 24 months. Discontinuation due to iRAEs were included. Effect sizes were pooled using a random-effects model using the meta and metafor packages in R after logit transformation. Inter-study heterogeneity was quantified using I2 statistic. Results: Systematic review yielded 34 studies investigating TFS in prospective and retrospective studies. Of these, three retrospective cohort studies reported real-world TFS at 12 and 24 months. Overall, 738 patients with advanced melanoma were included in this meta-analysis, with 384 patients in CR, 278 patients in PR, and 76 patients in SD at time of ICI discontinuation. Mean patient age was 66.4 and 61.9% of patients were male. Pooled 12 and 24-month TFS proportions were higher for patients with CR than PR and for patients with PR than SD. Pooled 24-month TFS was statistically significantly greater in patients with CR compared to SD. I2 statistics showed considerable heterogeneity between studies ( > 80% in CR and PR subgroups). Conclusions: 12 and 24-month TFS after ICI discontinuation was significant for patients with CR and PR to therapy, suggesting the feasibility of ICI discontinuation in patients after therapy response. Pooled 12-month TFS for patients with SD was 66%, although with decline to 36% at 24 months. Limitations of this meta-analysis include a limited number of included studies. Further research is needed to determine the optimal duration of ICI therapy for patients with advanced melanoma depending on best overall therapy response. [Table: see text]

Utidelone for heavily pretreated metastatic castration-resistant prostate cancer after failing docetaxel treatment: An open-label, single-arm, phase II trial.

e17036 Background: The appropriate chemotherapy for metastatic castration-resistant prostate cancer (mCRPC) that progressed after docetaxel treatment remains unmet medical needs. Utidelone (UTD1) is a genetically engineered epothilone analog with antitumor activity in taxane-resistant cancers. UTD1 was approved for advanced breast cancer in 2021. This study was designed to evaluate the safety and efficacy of UTD1 in mCRPC. Methods: In this perspective, phase II clinical trial, men with progressive mCRPC after docetaxel and abiraterone, and/or enzalutamide, and/or apalutamide received UTD1 monotherapy treatment at a total dose of 150 mg/m2 for five days intravenous, every three weeks until disease progression, or intolerable toxicity, or death. We reported the preliminary results for potential benefits in this new treatment. The primary endpoint was prostate specific antigen (PSA) response rate, defined as a 50% or greater reduction in serum PSA. The secondary endpoint included investigators-assessed objective response rate (ORR) and disease control rate (DCR) according to RECIST v1.1, radiographic progression-free survival (rPFS) according to PCWG3 criteria, overall survival (OS), and safety. The trial was registered at Chinese Clinical Trial Registry (No. ChiCTR2200061635). Results: By January 31st, 2024, twenty-five mCRPC patients with a median age of 67 years were enrolled in this study at Sun Yat-sen University Cancer Center since March 23rd, 2022. Patients received an average of 4.2 lines of prior anticancer treatments: 100% of them received docetaxel, 96.0% of them received abiraterone, and 80.0% progressed after enzalutamide, and/or apalutamide. 28.0% of patients had visceral metastases, and 88.0% patients had bone metastases. At of the cut-off date, the PSA response rate was 16.0%. The median rPFS and OS were 4.9 months and 7.1 months, respectively. One patient had a durable response for 19.2 months and had been remaining on study treatment to date. One PR and four SD were observed in ten patients with measurable lesions, resulting in an overall ORR and DCR of 10.0% and 50.0%, respectively. The most common treatment-related adverse events (TRAEs) including peripheral sensory neuropathy (76.0%), dyspepsia (72.0%), anemia (64.0%), constipation (60.0%), fatigue (64.0%), nausea (36.0%), leukocytopenia (32.0%), arthralgia (32.0%), dizziness (32.0%), vomiting (20.0%), and diarrhea (20.0%) were manageable. The 3/4 grade TRAEs included anemia (16.0%), and diarrhea (4%). No treatment-related death occurred. Conclusions: UTD1 has demonstrated promising efficacy and favorable tolerance in heavily pretreated mCRPC patients after progression on docetaxel in the preliminary analyses. Additional randomized trials are warranted for this new regimen. Clinical trial information: ChiCTR2200061635.

Association of combination tumor texture and vessel tortuosity with progression free survival across PD-L1 subgroups in durvalumab treated non-small cell lung cancer (NSCLC): Blinded validation results from CP1108.

8600 Background: Immunotherapy (IO) has shown a durable response with minimal toxicity in the treatment of metastatic NSCLC. However, only 30-50% of these patients (pts) actually respond. Despite initial optimism surrounding PD-L1 expression as a potential biomarker, IO provides benefit across PD-L1 low (<25%) and high (≥25%) status. This highlights a critical need for more effective biomarkers to guide treatment decisions. Here, we present blinded validation results of a CT-based biomarker of change in quantitative vessel tortuosity (1) (Δ-QVT) and texture radiomics (2) (Δ-Rad) between baseline (B) and 6 weeks post-treatment (TP1) for predicting response, overall survival (OS) and progression free survival (PFS) in CP1108 (NCT01693562). Methods: CT scans at B and TP1 were retrospectively analyzed from two studies (a) a multi-center training set (Str, N=110) of metastatic NSCLC pts treated with first line IO and (b) a blinded NSCLC cohort of N = 151 pts treated with Durvalumab in CP1108 study (Sv). In Sv, N=75 pts were PD-L1 high (Sv+) whereas N=65 pts were PD-L1 low (Sv-). An in-house MATLAB based algorithm was used to extract intra-tumoral, peri-tumoral texture and QVT features from up to two largest measurable tumors in each CT. A classifier (MCombo) was trained on Str to predict best overall response defined as per the RECIST v1.1 criteria using combination of Δ-QVT and Δ-Rad features. Area under the receiver operating characteristic (AUC) was used to evaluate MCombo against RECIST response whereas univariable and multivariable Cox regression models with log-rank test, hazard ratio (HR) with confidence interval (CI) and concordance index (C-index) were used to study the association of MCombo with OS and PFS in Sv, Sv+, and Sv-. Results: MCombo predicted objective response with an AUC of 0.78 in Sv and was statistically significantly associated with PFS (Table) in Sv, Sv+, and Sv-. MCombo was associated with OS in Sv, Sv+, but not in Sv-. Multivariable analysis with PD-L1 status, histological subtype, ECOG status, liver metastasis, line of therapy and sex showed independent association of MCombo across OS and PFS. Conclusions: Our results indicate that combination of radiomics and vessel tortuosity biomarker from CT is independently prognostic of response and PFS across PD-L1 levels. Prospective validation of this biomarker is needed. 1. Alilou et al. Sci Adv 2022. 2. Khorrami et al. Cancer Immunol Res 2020. [Table: see text]

Mosunetuzumab with polatuzumab vedotin: Subgroup analyses in patients (pts) with primary refractory or early relapsed large B-cell lymphoma (LBCL).

7021 Background: The primary analysis of mosunetuzumab with polatuzumab vedotin (mosun-pola) in the Phase Ib/II study (NCT03671018) demonstrated durable responses and manageable safety in pts with relapsed or refractory (R/R), transplant-ineligible LBCL (Budde et al. Nat Med 2023). Here, we present results for primary refractory (refr) or early relapse (rel) subgroups from this study after a median follow-up of 23.9 months. Methods: Pts with R/R LBCL (diffuse LBCL not otherwise specified [NOS], high-grade B-cell lymphoma [HGBCL], transformed follicular lymphoma (FL), and FL grade 3b) and who received ≥1 prior line of therapy (including an anti-CD20 antibody) were treated with mosun-pola. Refr was defined as SD, PD, PR, or CR with relapse <3 months after first-line (1L) therapy. Rel was defined as CR with relapse ≥3 and ≤12 months after 1L therapy. The primary endpoint was best overall response rate (ORR) by IRC using Lugano 2014 response criteria. Key secondary endpoints included CR rate, duration of response (DOR), duration of CR (DOCR), progression-free survival (PFS), overall survival (OS), and safety. Results: As of July 6, 2023, of the 98 pts in the overall population, 45 (46%) and 27 (28%) pts had refr or rel LBCL, respectively. At baseline, the median age in the refr and rel subgroups was 68 and 70 years respectively; 23/45 pts (51%) and 6/27 pts (22%) were treated with mosun-pola as second-line, respectively. The majority of refr/rel pts had DLBCL NOS (71%; 78%) or HGBCL (24%; 19%), Ann Arbor stage III/IV (80%; 89%), elevated LDH (55%; 48%), and extranodal involvement (67%; 59%). In refr pts, the ORR was 49%, which was generally consistent with the overall population (59%); although the sample size was limited, higher responses (ORR: 74%) were observed in rel pts. Additional clinical outcomes are reported (Table). The safety profile was consistent with the overall population. Grade 3 CRS occurred in one pt in each subgroup. Treatment-related ICANS-like events occurred in 2/45 pts (4%; refr) and 3/27 pts (11%; rel). Conclusions: Mosun-pola demonstrated durable benefits in ORR and CR rates irrespective of a poor response to 1L treatment. Outcomes for pts with refr or rel LBCL are encouraging. Clinical trial information: NCT03671018 . [Table: see text]

Efficacy and safety of lifileucel, an autologous tumor-infiltrating lymphocyte cell therapy, and pembrolizumab in patients with immune checkpoint inhibitor-naive unresectable or metastatic melanoma: Updated results from IOV-COM-202 cohort 1A.

9505 Background: Immune checkpoint inhibitors (ICI) are front-line standard-of-care treatment (tx) for advanced (unresectable or metastatic) melanoma. Despite recent advances in front-line tx, a majority of patients (pts) do not achieve long-term benefit. Lifileucel, a one-time autologous tumor-infiltrating lymphocyte (TIL) cell therapy, potentially induces durable responses in pts with advanced melanoma previously treated with ICI. This study evaluates lifileucel combined with anti-PD-1 therapy in front-line advanced melanoma. Methods: IOV-COM-202 (NCT03645928) Cohort 1A assesses the efficacy and safety of lifileucel and pembrolizumab (pembro) in pts with ICI-naive unresectable or metastatic melanoma. Pts may have received BRAF/MEK inhibitor tx if BRAF mutation-positive. Eligible pts must have ≥1 resectable lesion (≥1.5 cm diameter) for 22-day cryopreserved lifileucel manufacturing, and ≥1 measurable lesion for response assessment per RECIST v1.1. The tx regimen consists of pembro, nonmyeloablative lymphodepletion (cyclophosphamide and fludarabine), a single lifileucel infusion (1 × 109 – 150 × 109 cells), ≤6 doses of IL-2 (600,000 IU/kg IV), and continued pembro until disease progression, or unacceptable toxicity for ≤24 months. The endpoints are investigator-assessed objective response rate (ORR) and incidence of grade ≥3 treatment-emergent adverse events (TEAE). Results: As of 22-Dec-2023, 22 pts with a median (range) age of 48.5 (18–68) years received lifileucel and pembro. At baseline, the median (range) target lesion sum of diameters was 54.5 (14–355) mm; 7 (31.8%) pts had liver lesions. Metastatic staging at study entry was as follows: 4 (18.2%) had M1a, 2 (9.1%) had M1b, 10 (45.5%) had M1c, and 2 (9.1%) had M1d. Eight (36.4%) pts had V600 BRAF mutations; 3 (13.6%) pts had prior BRAF/MEK inhibitor tx. Confirmed ORR was 63.6% (14/22), including 22.7% (5/22) CR and 40.9% (9/22) PR; 6 pts (27.3%) had SD. Median time to initial response was 2.5 months. All response evaluable pts demonstrated regression of target lesions. At a median follow-up of 17.2 months, median duration of response was not reached. Responses deepened over time; 10/14 (71.4%) pts had ongoing response and 8/14 (36.4%) pts had response ≥12 months. TEAEs were consistent with the underlying disease and known safety profiles of pembro, nonmyeloablative lymphodepletion, and IL-2. Most common grade ≥3 TEAEs were thrombocytopenia (68.2%), neutropenia (50.0%), and anemia (45.5%). Conclusions: These results demonstrate encouraging efficacy and durability for the combination of lifileucel and pembro and support its further evaluation in pts with untreated advanced melanoma in the phase 3 study TILVANCE-301 (NCT05727904). Clinical trial information: NCT03645928 .

Comparative analysis of first-line therapy with fruquintinib plus chemotherapy versus standard therapy in advanced metastatic colorectal cancer (mCRC): A prospective cohort study compared with propensity score matching (PSM) cohort.

3591 Background: We have previously reported that fruquintinib plus mFOLFOX6/FOLFIRI as the first-line therapy followed by fruquintinib plus capecitabine maintenance (FRU regimens) for advanced mCRC patients (pts) showed durable response and a favorable safety profile in this prospective, open-label, multicenter, single-arm phase 2 study (NCT05004441). We retrospectively collected matching data of standard therapy (STD regimens: bevacizumab/cetuximab plus chemotherapy) as the first-line treatment to compare with longer follow-up data in this study. Methods: Pts diagnosed with unresectable or metastatic CRC pts excluded BRAF mutations (Mut) were enrolled to receive FRU regimens. We collected retrospective data that pts who met our eligibility criteria receiving STD regimens as historical control data. PSM was performed to adjust potential confounders between two regimens. PSM was conducted on the basis of 4 clinically relevant variables (tumor location, RAS/BRAF status, liver metastasis). Efficacy was recorded and compared. Safety from FRU regimens was calculated and reported as well. Results: From Jul 22, 2021 to May 30, 2023, 43 pts were enrolled (median age 57 [range: 37-74], 27 male, 25 harboring RAS Mut, 26 with liver metastases) in FRU regimens. We retrospectively collected 63 pts received STD regimens with 38% (24/63) RAS Mut. There was no significant difference in the baseline between two regimens. Up to Jan 15, 2024, before applying the PSM, pts received FRU regimens were benefit with a higher ORR than STD regimens (83.33% vs 61.90%, p=0.018, OR=3.077, 95%CI: 1.181-8.017), especially RAS Mut pts (87.50% vs 58.33%, p=0.051). The median PFS was 16.76 mo (95%CI 12.25-18.6) in FRU regimens, which was significantly longer than 10.38 mo of STD regimens (p=0.0115). Favorable PFS was observed in RAS Mut pts received FRU regimens compared with STD regimens (14.16 mo vs 10.48 mo, p=0.1635). After 1:1.5 PMS, pts with FRU regimens showed a significantly improvement in median PFS compared with STD regimens (15.9mo vs 11.3mo, p=0.020, HR=0.472, 95%CI: 0.251-0.889). Safety profile exhibited the FRU regimens was tolerable and main TEAEs were grade 1/2. Most common grade 3/4 TEAEs were neutrophil count decreased (18.60%), leukopenia (16.28%) and lymphocytopenia (6.98%). Only one serious AE reported with gastric perforation recovered after non-operative therapy. Conclusions: The fruquintinib combination regimens as a first-line therapy for pts with mCRC significantly improved median PFS compared to standard treatment. Similar to the primary analysis, the safety profile was generally manageable with longer duration of treatment exposure. Fruquintinib combined with mFOLFOX6/FOLFIRI might be a more promising treatment option as first-line therapy for mCRC pts. Clinical trial information: NCT05004441 .

Synergistic antitumor activity of METTL3 peptide degrader and immune checkpoint inhibitor in advanced urothelial cancer.

e14623 Background: In patients afflicted with advanced urothelial carcinoma (aUC), the durable response rate to immune checkpoint inhibitor (ICI) is approximately 20%. Recent study showed the pivotal role of N6-methyladenosine (m6A) methyltransferase-like 3 (METTL3) in immune escape and the progression of aUC. This study aimed to develop a novel METTL3 peptide degrader RKL and investigate its synergistic effects and underlying mechanisms in combination with ICI for aUC. Methods: Methyltransferase expression profiles were scrutinized using The Cancer Genome Atlas database; while the prognostic implications of METTL3 expression in response to ICI were analyzed in the IMvigor210 cohort study. Single-cell RNA sequencing (scRNA-seq) was employed to elucidate the mechanistic insights. The METTL3 peptide degrader RKL was synthesized using Fmoc solid-phase peptide synthesis and purified with high-performance liquid chromatography. In vivo and in vitro experiments were conducted to assess the impact of RKL, ICI, and their combination on aUC inhibition. Results: In aUC, METTL3 exhibited the most significant up-regulation among m6A methyltransferases, while METTL14 and WTAP showed down-regulated expression. In the IMvigor210 cohort study, aUC patients with elevated METTL3 expression and treated with ICI demonstrated a poorer prognosis. scRNA-seq revealed that METTL3 upregulation promoted the expression of genes regulating cancer-associated fibroblast proliferation, contributing to enhanced tumor resistance to immunotherapy. RKL demonstrated high toxicity to urothelial carcinoma cell lines, inhibiting their proliferative, migratory, and invasive capacities in vitro. The combined treatment of RKL and ICI significantly reduced tumor volume (P<0.001), with a complete response achieved in 87.5% (7/8) of mice in the combination group, 12.5% (1/8) in the RKL group, and 25.0% (2/8) in the ICI group. Conclusions: METTL3 overexpression in aUC is associated with immune escape and resistance to ICI therapy. The METTL3 peptide degrader RKL, when combined with ICI, demonstrates synergistic antitumor effects in aUC, warranting further exploration in clinical research.

Concurrent enhancer of Zeste homolog 2 (EZH2) over-expression with BRAFV600E mutation predicts a poor outcome in patients with Langerhans cell histiocytosis (LCH): A pilot study.

e18536 Background: Prior studies demonstrated upregulated EZH2 protein expression and p-ERK1/2 cascade signaling in histiocytic and dendritic cell neoplasms. BRAFV600E is the most common driver mutation reported in LCH patients (34-64%). In melanoma studies, a signaling pathway with BRAFV600E activating mutation resulted in upregulation of EZH2. The frequency of EZH2 co-expression with BRAFV600E is unknown in LCH. Given the limited durable responses after discontinuation of treatment with BRAF inhibitors in histiocytic disorders, we investigated the prognostic role of EZH2 overexpression and BRAFV600E mutation in LCH. Methods: We analyzed a cohort of 27 consecutive patients (pts) diagnosed with LCH at Moffitt Cancer Center and Tampa General Hospital between 2010-2022. Immunohistochemical (IHC) staining using antibodies against EZH2 (D2C9 clone, Cell Signaling) and BRAFV600E (VE1 clone, Ventana medical systems) were performed. Expression was assessed by an IHC score of stain intensity (0, 1+, 2+ and 3+) multiplied by percent positive cells (H score). H score ≥ 30 was considered as positive. Pyrosequencing was performed to detect BRAFV600E mutations and correlated with VE1 staining results. A positive outcome from either IHC or PCR was deemed indicative of mutation positivity, given the robust presence of mutation representation in melanoma studies through IHC. Results: Entire cohort were grouped for pts who had both EZH2 overexpression and BRAFV600E mutation (EZH2/BRAFV600E) versus those who did not. Out of 27 pts, 25.9% (n=7) had both EZH2/BRAFV600E. EZH2/BRAFV600E group differed from control group by age ( p=0.046). BRAFV600E mutation was identified in 37.03% (10) pts, and 40.7% (11) showed expression of VE1 by IHC study. Discrepancies between PCR and IHC study were observed in 4 pts and potentially attributable to the restricted availability of tissue samples. 63% and 48.1% of pts were positive for EZH2 and BRAFV600E respectively. 6 pts were observed, 8 underwent surgery with or without radiation, 12 received induction chemotherapy, and only 1 received a BRAF inhibitor. After 18.6 months of median follow up, 92.6% pts were alive. Overall response rate (ORR) to the 1st line therapy was 55.6%. In univariate analysis of OS, H score and BRAFV600E mutation trended towards worse OS but were not statistically significant owing to small sample size. However, BRAFV600E mutation and EZH2 over expression demonstrated a poor overall survival (OS) ( p=0.012). Conclusions: Our study indicates that concurrent presence of BRAFV600E mutation and EZH2 overexpression correlates with poor OS in LCH pts. We hypothesize that in a subset of LCH pts combination therapy targeting both EZH2 and BRAFV600E may improve ORR or overcome resistance to BRAF inhibitor monotherapy. However, the results of our pilot study need to be validated on a larger sample set.

Advanced renal cell cancer combination immunotherapy clinical trial (ARCITECT; HCRN GU 22-587).

TPS4614 Background: First-line treatment for patients with metastatic clear cell renal cell carcinoma (mccRCC) often includes an anti-PD1 inhibitor in combination with either an anti-CTLA inhibitor (IO/IO) or a VEGF receptor tyrosine kinase inhibitor (TKI) (IO/TKI). Although some patients treated with nivolumab/ipilimumab (Nivo/Ipi) (IO/IO) experience durable responses leading to treatment free intervals, over two-thirds experience disease progression. Resistance to Nivo (anti-PD1) monotherapy has been associated with increased presence of a subpopulation of Tregs in the tumor microenvironment. Botensilimab (Bot) is an IO agent that leverages novel FcyR-associated mechanisms of action to enhance T cell priming, deplete intratumoral Tregs and enhance myeloid activation. Combination botensilimab/balstilimab (Bot/Bal) (anti-CTLA/anti-PD1) has shown impressive anti-tumor activity in diseases where Nivo/Ipi has shown little to no efficacy. Methods: ARCITECT is a phase II, multicenter investigator initiated trial evaluating the efficacy and safety of Bot/Bal relative to Nivo/Ipi. Patients with mccRCC (favorable, intermediate, or poor risk), no prior systemic therapy (including adjuvant or neoadjuvant), and at least one measurable lesion as defined by RECIST 1.1 are eligible for enrollment. 120 patients will be randomized in a 2:1 fashion to Arm A (Bot/Bal induction followed by Bal maintenance) or Arm B (Nivo/Ipi induction followed by Nivo maintenance) each for a maximum of 2 years. Stratification factors include IMDC risk groups and sarcomatoid histology. The primary endpoint is overall response rate (ORR) per RECIST 1.1. We hypothesize that Bot/Bal will lead to a superior ORR (55%) relative to Nivo/Ipi (40%). This trial has > 90% power to detect the alternative hypothesis while maintaining a one-sided significance level of not more than 0.10 using the exact binomial. The study will be monitored for early stopping in favor of the null hypothesis based on a Simon’s two stage design. In the first stage, 69 patients will be enrolled (Arm A:46 and Arm B:23). If at the end of the first stage, Arm A has either at least 18/42 (42.8%) of eligible patients responding or an ORR at least numerically equivalent to that for eligible patients in Arm B, then the trial will progress to the second stage. The primary endpoint will be met if there are 38/80 responders (ORR > 47.5%) in Arm A. Key secondary endpoints include landmark progression-free survival, treatment-free survival and rates of immune-related adverse events. Correlative studies will explore immune and molecular predictors of response and resistance to IO/IO in tumor and blood. Clinical trial information: NCT05928806 .

Long-term follow-up of ARI0002h (cesnicabtagene autoleucel), an academic point-of-care B-cell maturation antigen (BCMA)-directed chimeric antigen receptor (CAR) T-cell strategy: Activity and safety after fractionated initial therapy and booster dose in 60 patients with relapsed/refractory multiple myeloma (RRMM).

7544 Background: The activity and safety ofARI0002h, an academic autologous CAR T-cell product with a humanized single chain variable fragment targeting BCMA has been reported in a pilot multicenter clinical trial (CARTBCMA-HCB-01) treating 30 patients (pts) with RRMM (NCT04309981) (Oliver-Caldés, Lancet Onc 2023). Here, we describe results of the final cohort of 60 pts with longer follow-up. Methods: Patients aged 18-75 years old with RRMM were eligible if they had measurable disease, were refractory to the last line of treatment and received ≥2 prior regimens, including a proteasome inhibitor, an immunomodulatory drug and an anti-CD38 antibody. The target dose (3x106/kg CAR+cells) was administered in a fractionated manner (10%/30%/60%). A second dose of up to 3x106 CAR+ cells/kg was planned at least 3 months after the first dose in pts with any kind of response and no limiting side effects. Primary endpoints were overall response rate (ORR) within the first 3 months and rate of cytokine release syndrome (CRS) and/or neurotoxicity in the first 30 days. Bone marrow minimal residual disease (MRD) was analyzed by next-generation flow at a sensitivity of 10-6. Results: As of December 18th 2023, 72 pts with RRMM were screened, 69 underwent apheresis and 61 received LD, with 60 pts finally receiving ARI0002h. The ORR in the first 3 months was 95% (≥ very good partial response (VGPR) in 77%). Median time to first response was one month. Responses deepened over time, achieving 58% complete response (CR) (55% stringent CR). MRD-negative rates on evaluable samples on days 28 and 100 were 98% and 96%, respectively. With a median follow-up of 24 months (95%CI 9.8-39.9), estimated median progression-free survival (PFS) was 20 months (95% CI 13.2-26.8). Median overall survival (OS) was not reached with OS rate at 24 months of 63%. CRS was observed in 90% with 5% grades ≥ 3. Median time to CRS was 7 days (1-14) with a median duration of 4.5 days. Mild acute neurotoxicity was reported in only 2 pts (3%) with no late neurologic events. 6 pts (10%) developed a macrophage activation syndrome (4 grades 1-2, 1 grade 3, 1 grade 5). Seven patients (11.7%) developed second primary malignancies after ARI0002h infusion, including 3 skin cancers (one in situ melanoma), 3 solid tumors and one acute myeloid leukemia. 80% (44 out of 5) eligible pts had already received the booster dose, with no relevant toxicities. Median time after first infusion was 4.4 months. Response was evaluable in 42 pts; 45% (n=19) were already in sCR, 29% (n=12) maintained the response and 26% (n=11) improved the response. Conclusions: Results from 60 pts and a longer follow-up confirm the safety profile and the deep and durable responses obtained after ARI0002h infusion. Clinical trial information: NCT04309981 .