Magrolimab in Combination With Azacitidine in Patients With Higher-Risk Myelodysplastic Syndromes: Final Results of a Phase Ib Study.

PURPOSE: Magrolimab is a monoclonal antibody that blocks cluster of differentiation 47, a don't-eat-me signal overexpressed on cancer cells. Cluster of differentiation 47 blockade by magrolimab promotes macrophage-mediated phagocytosis of tumor cells and is synergistic with azacitidine, which increases expression of eat-me signals. We report final phase Ib data in patients with untreated higher-risk myelodysplastic syndromes (MDS) treated with magrolimab and azacitidine (ClinicalTrials.gov identifier: NCT03248479). PATIENTS AND METHODS: Patients with previously untreated Revised International Prognostic Scoring System intermediate-/high-/very high-risk MDS received magrolimab intravenously as a priming dose (1 mg/kg) followed by ramp-up to a 30 mg/kg once-weekly or once-every-2-week maintenance dose. Azacitidine 75 mg/m2 was administered intravenously/subcutaneously once daily on days 1-7 of each 28-day cycle. Primary end points were safety/tolerability and complete remission (CR) rate. RESULTS: Ninety-five patients were treated. Revised International Prognostic Scoring System risk was intermediate/high/very high in 27%, 52%, and 21%, respectively. Fifty-nine (62%) had poor-risk cytogenetics and 25 (26%) had TP53 mutation. The most common treatment-emergent adverse effects included constipation (68%), thrombocytopenia (55%), and anemia (52%). Median hemoglobin change from baseline to first postdose assessment was -0.7 g/dL (range, -3.1 to +2.4). CR rate and overall response rate were 33% and 75%, respectively. Median time to response, duration of CR, duration of overall response, and progression-free survival were 1.9, 11.1, 9.8, and 11.6 months, respectively. Median overall survival (OS) was not reached with 17.1-month follow-up. In TP53-mutant patients, 40% achieved CR with median OS of 16.3 months. Thirty-four patients (36%) had allogeneic stem-cell transplant with 77% 2-year OS. CONCLUSION: Magrolimab + azacitidine was well tolerated with promising efficacy in patients with untreated higher-risk MDS, including those with TP53 mutations. A phase III trial of magrolimab/placebo + azacitidine is ongoing (ClinicalTrials.gov identifier: NCT04313881 [ENHANCE]).

Single-Agent Mosunetuzumab Shows Durable Complete Responses in Patients With Relapsed or Refractory B-Cell Lymphomas: Phase I Dose-Escalation Study.

PURPOSE: Mosunetuzumab is a bispecific antibody targeting CD20 and CD3 that redirects T cells to engage and eliminate malignant B cells and is being developed for relapsed or refractory (R/R) B-cell non-Hodgkin lymphomas (B-NHLs). METHODS: This first-in-human trial (ClinicalTrials.gov identifier: NCT02500407) evaluated the safety and tolerability and efficacy of mosunetuzumab in patients with R/R B-NHL and established the recommended phase II dose. Data from dose escalation are presented. Single-agent mosunetuzumab was administered intravenously in 3-week cycles, at full dose in cycle 1 day 1 (group A) or with ascending (step-up) doses during cycle 1 on days 1, 8, and 15 (group B), for eight or 17 cycles on the basis of tumor response. RESULTS: Two hundred thirty patients were enrolled. Doses up to 2.8 mg and 60 mg were assessed in groups A and B, respectively; maximum tolerated dose was not exceeded. In group B (n = 197), common adverse events (≥ 20% of patients) were neutropenia (28.4%), cytokine release syndrome (27.4%), hypophosphatemia (23.4%), fatigue (22.8%), and diarrhea (21.8%). Cytokine release syndrome was mostly low-grade (grade ≥ 3: 1.0%) and mainly confined to cycle 1. Across the doses investigated (group B), best overall response rates were 34.9% and 66.2% in patients with aggressive and indolent B-NHL, respectively, and complete response rates were 19.4% and 48.5%. Among patients with a complete response, the median duration of response was 22.8 months (95% CI, 7.6 to not estimable) and 20.4 (95% CI, 16 to not estimable) in patients with aggressive and indolent B-NHL, respectively. CONCLUSION: Mosunetuzumab, administered with step-up dosing, has a manageable safety profile and induces durable complete responses in R/R B-NHL. The expansion stage of the study is ongoing at the dose level of 1/2/60/60/30 mg selected for further study.

Safety and Clinical Activity of Atezolizumab in Patients with Metastatic Castration-Resistant Prostate Cancer: A Phase I Study.

PURPOSE: Atezolizumab [anti-programmed death-ligand 1 (anti-PD-L1)] is well tolerated and efficacious in multiple cancers, but has not been previously evaluated in metastatic castration-resistant prostate cancer (mCRPC). This study examined the safety, efficacy, and biomarkers of atezolizumab monotherapy for mCRPC. PATIENTS AND METHODS: This phase Ia, open-label, dose-escalation and dose-expansion study (PCD4989g) enrolled patients with mCRPC who had progressed on sipuleucel-T or enzalutamide. Atezolizumab was given intravenously every 3 weeks until confirmed disease progression or loss of clinical benefit. Prespecified endpoints included safety, efficacy, biomarker analyses, and radiographic assessments. RESULTS: All 35 evaluable patients [median age, 68 years (range, 45-83 years)] received atezolizumab after ≥1 prior line of therapy; 62.9% of patients had received ≥3 prior lines. Treatment-related adverse events occurred in 21 patients (60.0%), with no deaths. One patient had a confirmed partial response (PR) per RECIST 1.1, and 1 patient had a PR per immune-related response criteria. The confirmed 50% PSA response rate was 8.6% (3 patients). Median overall survival (OS) was 14.7 months [95% confidence interval (CI): 5.9-not evaluable], with a 1-year OS rate of 52.3% (95% CI: 34-70); 2-year OS was 35.9% (95% CI: 13-59). Median follow-up was 13.0 months (range, 1.2-28.1 months). Biomarker analyses showed that atezolizumab activated immune responses; however, a composite biomarker failed to reveal consistent correlations with efficacy. CONCLUSIONS: Atezolizumab was generally well tolerated in patients with mCRPC, with a safety profile consistent with other tumor types. In heavily pretreated patients, atezolizumab monotherapy demonstrated evidence of disease control; however, its limited efficacy suggests a combination approach may be needed.

Clinical Activity and Safety of Atezolizumab in a Phase 1 Study of Patients With Relapsed/Refractory Small-Cell Lung Cancer.

BACKGROUND: Programmed death-ligand 1 (PD-L1) protein is expressed in various cancers, including small-cell lung cancer (SCLC). Atezolizumab inhibits PD-L1 signaling, thus restoring tumor-specific T-cell immunity. Here, we report results from the first-in-human phase 1 PCD4989g study (NCT01375842) of atezolizumab, in a cohort of patients with relapsed/refractory SCLC. PATIENTS AND METHODS: Eligible patients with incurable or metastatic SCLC, which was advanced or recurrent since the last antitumor therapy, received atezolizumab 15 mg/kg or 1200 mg intravenously every 3 weeks for 16 cycles or until loss of clinical benefit. The primary endpoint was safety. Efficacy and biomarkers of antitumor activity were also assessed. RESULTS: Seventeen patients were enrolled. Any-grade and grade ≥3 treatment-related adverse events (TRAEs) occurred in 11 (64.7%) and 5 (29.4%) patients, respectively. The most common any-grade TRAE was fatigue (4 patients [23.5%]). Partial response to atezolizumab was achieved in 1 patient (5.9%) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1), and 3 (17.6%) per immune-related response criteria (irRC). Durations of response were 2.8 to > 45.7 months. Median investigator-assessed progression-free survival (PFS) per RECIST v1.1 and irRC was 1.5 (95% confidence interval [CI], 1.2-2.7) and 2.9 (95% CI, 1.2-6.1) months, respectively. Median overall survival (OS) was 5.9 months (95% CI, 4.3-12.6). Patients with high (≥ median expression) T-effector gene signature and PD-L1 mRNA expression appeared to show a trend toward improved PFS (per irRC) and OS. CONCLUSION: Atezolizumab was generally well tolerated and exhibited antitumor activity in a small cohort of patients with relapsed/refractory SCLC.

Tumor immune microenvironment and genomic evolution in a patient with metastatic triple negative breast cancer and a complete response to atezolizumab.

BACKGROUND: Metastatic TNBC (mTNBC) has a poor prognosis and few treatment options. The anti-PD-L1 antibody atezolizumab demonstrated clinical activity in mTNBC patients with PD-L1-positive tumor-infiltrating immune cells. The current study describes the tumor immune microenvironment (TiME) and genomic evolution across sequential therapies in a patient with a 31-year history of TNBC and a complete response (CR) to atezolizumab monotherapy. MATERIALS AND METHODS: In 1986, the patient had surgery and radiotherapy (XRT) for newly diagnosed TNBC, followed by surgery and adjuvant chemotherapy for two locoregional recurrences. She developed mTNBC in 2009 and was sequentially treated with capecitabine, gemcitabine-carboplatin-iniparib (GCI), XRT and an experimental vaccine. She experienced disease progression (PD) to all these therapies. In 2013, she had a PD-L1 positive tumor and enrolled in a phase 1 atezolizumab monotherapy study (PCD4989g; NCT01375842). She received atezolizumab for 1 year with initial pseudo-progression followed by a partial response. After 1 year without treatment she experienced PD, reinitiated atezolizumab and subsequently achieved CR. Tumor specimens were collected at numerous times between 2008 and 2015 and assessed by immunohistochemistry, RNA-seq and DNA-seq. RESULTS: TiME biomarkers, including CD8, ICs and PD-L1 on IC, increased after capecitabine and remained high after GCI, XRT and through pseudo-progression on atezolizumab. At PD post-atezolizumab exposure, TiME biomarkers decreased but PD-L1 status remained positive. Immune-related RNA signatures confirmed these findings. TNBC subtyping revealed evolution from luminal androgen receptor (LAR) to basal-like immune activated (BLIA). Genomic profiling showed truncal alterations in RB1 and TP53, while the presence of other genomic alterations varied over time. Tumor mutational burden peaked after XRT and declined after atezolizumab exposure. CONCLUSIONS: This case report describes the evolution of TiME and TNBC molecular subtypes/genomics over time with sequential therapies in a TNBC patient with a CR to atezolizumab monotherapy. These data suggest the TiME is pliable and may be manipulated to maximize response to immunotherapy (NCT01375842, https://clinicaltrials.gov/ct2/show/NCT01375842?term=NCT01375842&rank=1 ).

Safety, Clinical Activity, and Biological Correlates of Response in Patients with Metastatic Melanoma: Results from a Phase I Trial of Atezolizumab.

PURPOSE: Atezolizumab [anti-programmed death-ligand 1 (PD-L1)] selectively targets PD-L1 to block its interaction with receptors programmed death 1 and B7.1, thereby reinvigorating antitumor T-cell activity. We evaluated the long-term safety and activity of atezolizumab, along with biological correlates of clinical activity endpoints, in a cohort of patients with melanoma in an ongoing phase Ia study (NCT01375842). PATIENTS AND METHODS: Patients with unresectable or metastatic melanoma were enrolled to receive atezolizumab 0.1 to 20 mg/kg or ≥10 mg/kg every 3 weeks. Primary study objectives were safety and tolerability. Secondary objectives included investigator-assessed efficacy measures; pharmacodynamic and predictive biomarkers of antitumor activity were explored. RESULTS: Forty-five patients were enrolled and were evaluable for safety. Most treatment-related adverse events (AE) were grade 1/2 (60%). Fatigue (44%), pruritus (20%), pyrexia (18%), and rash (18%) were the most common treatment-related AEs of any grade. No treatment-related deaths occurred. Overall response rate was 30% among 43 efficacy- evaluable patients, with a median duration of response of 62 months [95% CI, 35-not estimable (NE)]. Clinically meaningful long-term survival was observed, with a median overall survival of 23 months (95% CI, 9-66). Baseline biomarkers of tumor immunity [PD-L1 expression on immune cells, T effector (Teff), and antigen presentation gene signatures) and tumor mutational burden (TMB) were associated with improved response, progression-free survival, and overall survival. CONCLUSIONS: Atezolizumab was well tolerated, with durable responses and survival in patients with melanoma. PD-L1 expression, TMB, and Teff signatures may indicate improved benefit with atezolizumab in these patients.

Safety, clinical activity and biomarker assessments of atezolizumab from a Phase I study in advanced/recurrent ovarian and uterine cancers.

OBJECTIVE: Patients with advanced/recurrent epithelial ovarian and uterine cancers have limited treatment options beyond platinum chemotherapy. Both tumor types can express programmed death-ligand 1 (PD-L1), providing a potential therapeutic target for these patients. Here we present data from the ovarian and uterine cancer cohorts of the Phase I atezolizumab monotherapy study (PCD4989g). METHODS: This Phase I, multi-center, first-in-human, open-label, dose-escalation/expansion clinical trial investigated single-agent atezolizumab in cohorts of patients with recurrent epithelial ovarian or uterine cancer. The primary objective was to evaluate the safety and tolerability of single-agent atezolizumab. Anti-tumor activity and preliminary assessment of potential biomarkers were evaluated as secondary and exploratory objectives, respectively. RESULTS: The ovarian and uterine cancer cohorts enrolled 12 and 15 patients, respectively (10 [83%] and 5 [33%], respectively, had PD-L1 ≥ 5% on tumor-infiltrating immune cells). Atezolizumab was generally well tolerated with no new safety signals identified. The safety profiles in both cohorts were consistent with the known profile of atezolizumab monotherapy. Treatment-related adverse events (AEs) were mostly Grade ≤ 2, with no treatment-related Grade ≥ 4 AEs reported. Preliminary anti-tumor activity, with long durations of response, was observed in 2 patients from each cohort (ovarian cancer, 8.1 and 30.6+ months; uterine cancer, 7.3 and 16.6+ months). High microsatellite instability and tumor mutational burden were noted in the responders from the uterine cancer cohort. CONCLUSIONS: Atezolizumab monotherapy was well tolerated in patients with epithelial ovarian or uterine cancer and may have clinical activity warranting further investigation. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01375842.

Atezolizumab in patients with advanced non-small cell lung cancer and history of asymptomatic, treated brain metastases: Exploratory analyses of the phase III OAK study.

OBJECTIVES: To assess the safety and efficacy of atezolizumab and docetaxel in patients with and without a history of asymptomatic, treated brain metastases in the phase III OAK trial. MATERIALS AND METHODS: Patients received 1200 mg atezolizumab or 75 mg/m2 docetaxel every 3 weeks until unacceptable toxicity, disease progression, or loss of clinical atezolizumab benefit. Patients with asymptomatic, treated supratentorial metastases were eligible. Patients had brain scans before enrollment; follow-up brain scans and treatment were required when clinically indicated. RESULTS: Approximately 14% of patients in each arm had a history of asymptomatic, treated brain metastases (61/425 in the atezolizumab arm and 62/425 in the docetaxel arm). Fewer treatment-related adverse events (AEs), serious AEs, and treatment-related neurologic AEs were reported with atezolizumab than with docetaxel, regardless of history of asymptomatic, treated brain metastases. In patients with a history of asymptomatic, treated brain metastases, median overall survival (OS) was longer with atezolizumab than with docetaxel (16.0 vs 11.9 months; hazard ratio = 0.74; 95% CI: 0.49-1.13). Median OS was also longer with atezolizumab in patients without a history of asymptomatic, treated brain metastases (13.2 vs 9.3 months; hazard ratio = 0.74; 95% CI: 0.63-0.88). Landmark analyses showed that patients with a history of asymptomatic, treated brain metastases had a lower probability of developing new symptomatic brain lesions with atezolizumab vs docetaxel at 6-24 months. Patients without a history had a lower probability with atezolizumab at 18-24+ months. CONCLUSION: Atezolizumab had an acceptable neurologic safety profile, showed a trend toward an OS benefit, and led to a prolonged time to radiographic identification of new symptomatic brain lesions compared with docetaxel in patients who had a history of asymptomatic, treated brain metastases. Clinicaltrials.gov registration number: NCT02008227.

Long-term Clinical Outcomes and Biomarker Analyses of Atezolizumab Therapy for Patients With Metastatic Triple-Negative Breast Cancer: A Phase 1 Study.

Importance: Atezolizumab (anti-programmed cell death ligand 1 [PD-L1]) is well tolerated and clinically active in multiple cancer types. Its safety and clinical activity in metastatic triple-negative breast cancer (mTNBC) has not been reported. Objective: To evaluate the safety, clinical activity, and biomarkers associated with the use of single-agent atezolizumab in patients with mTNBC. Design, Setting, and Participants: Women with mTNBC (defined by investigator assessment) were enrolled between January 2013 and February 2016 in a multicohort open-label, phase 1 study at US and European academic medical centers. Median follow-up was 25.3 months (range, 0.4-45.6 months). Eligible patients regardless of line of therapy had measurable disease by Response Evaluation Criteria in Solid Tumors, version 1.1; Eastern Cooperative Oncology Group performance status of 0 to 1; and a representative tumor sample for assessment of immune cell (IC) PD-L1 expression. Interventions: Atezolizumab was given intravenously every 3 weeks until unacceptable toxic effects or loss of clinical benefit. Main Outcomes and Measures: Primary outcome was safety and tolerability. Activity and exploratory outcomes included objective response rate (ORR), duration of response, progression-free survival (PFS), and overall survival (OS). Outcomes were assessed in all patients and in key patient subgroups. Results: Among 116 evaluable patients (median age, 53 years [range, 29-82 years]), treatment-related adverse events occurred in 73 (63%); 58 (79%) were grade 1 to 2. Most adverse events occurred within the first treatment year. The ORRs were numerically higher in first-line (5 of 21 [24%]) than in second-line or greater patients (6 of 94 [6%]). Median duration of response was 21 months (range, 3 to ≥38 months). Median PFS was 1.4 (95% CI, 1.3-1.6) months by RECIST and 1.9 (95% CI, 1.4-2.5) months by irRC. In first-line patients, median OS was 17.6 months (95% CI, 10.2 months to not estimable). Patients with PD-L1 expression of at least 1% tumor-infiltrating ICs had higher ORRs and longer OS (12% [11 of 91]; 10.1 [95% CI, 7.0-13.8] months, respectively) than those with less than 1% ICs (0 of 21; 6.0 [95% CI, 2.6-12.6] months, respectively). High levels of ICs (>10%) were independently associated with higher ORRs and longer OS. Conclusions and Relevance: Single-agent atezolizumab was well tolerated and provided durable clinical benefit in patients with mTNBC with stable or responding disease and in earlier lines of treatment. Trial Registration: ClinicalTrials.gov identifier: NCT01375842.

Association of Cancer Immunotherapy With Acute Macular Neuroretinopathy and Diffuse Retinal Venulitis.

Importance: Checkpoint inhibition in cancer immunotherapy related to T-cell-driven mechanisms of action associated with acute macular neuroretinopathy (AMN) and diffuse retinal venulitis, an adverse event not previously described, is reported here. Objective: To describe 2 patients who developed ophthalmologic events after treatment with the programmed death 1 axis inhibitor, atezolizumab. Design, Setting, and Participants: Retrospective review of 2 patients treated with atezolizumab for metastatic breast cancer and colon cancer, respectively, who presented with AMN and diffuse retinal venulitis conducted at 2 tertiary medical centers. Main Outcomes and Measures: Multimodal imaging including near infrared, optical coherence tomography, and fluorescein angiography were used to characterize retinal vascular abnormalities. Results: Based on optical coherence tomography and multimodal imaging findings, the clinical diagnosis of AMN associated with diffuse retinal venulitis was made in these 2 patients receiving atezolizumab. Conclusions and Relevance: While only 2 cases of patients receiving the programmed death ligand 1 inhibitor atezolizumab who experienced AMN and diffuse retinal venulitis are described here, these findings suggest that patients receiving programmed death 1 axis inhibitor therapies may need to be monitored for unexpected immune-related ocular toxicity including abnormalities of the microvasculature and large retinal vessels. Further studies might investigate the potential mechanisms of retinal vascular changes associated with these therapies.

Clinical activity and safety of atezolizumab in patients with recurrent glioblastoma.

PURPOSE: Glioblastoma is the most common primary malignant brain tumor. No standard treatment exists for recurrent disease. Glioblastoma is associated with an immunosuppressive tumor microenvironment. Immune checkpoint inhibitors, including atezolizumab (anti-programmed death-ligand 1), have demonstrated clinical activity in various cancers. Here, we present the safety and efficacy of atezolizumab in patients with glioblastoma from the phase 1a PCD4989g clinical trial (NCT01375842). METHODS: Eligible patients had confirmed recurrent glioblastoma and measurable disease per RANO criteria. Atezolizumab (1200 mg) was administered intravenously every 3 weeks until progression or unacceptable toxicity. Patients were monitored for safety; response was evaluated at least every 6 weeks. Baseline biomarkers were evaluated. RESULTS: All 16 patients enrolled had received prior chemotherapy, and 50% prior bevacizumab. Ten patients (63%) experienced a treatment-related event. No treatment-related grade 4-5 events were reported. All deaths occurred due to progression or during follow-up. One patient experienced a partial response (5.3 months); 3 experienced disease stabilization. The median overall survival was 4.2 months (range 1.2 to 18.8+ months). Association between peripheral CD4+ T cells and efficacy was observed. Two patients with IDH1-mutant tumors and 1 with a POLE-mutant tumor experienced ≥ 16 months survival. CONCLUSIONS: Atezolizumab was safe and well tolerated in this group of patients with recurrent glioblastoma. Our preliminary findings suggest that biomarkers, including peripheral CD4+ T cells and hypermutated tumor status, may help guide selection of patients with recurrent glioblastoma who might receive most benefit from atezolizumab therapy, supporting further atezolizumab combination studies in glioblastoma.

Safety and clinical activity of atezolizumab monotherapy in metastatic non-small-cell lung cancer: final results from a phase I study.

INTRODUCTION: Atezolizumab, an anti-programmed death-ligand 1 (PD-L1) antibody, inhibits PD-L1:PD-1 and PD-L1:B7.1 interactions, restoring anticancer immunity. Here, we report final analyses from the non-small-cell lung cancer (NSCLC) cohort of the first atezolizumab phase I study. METHODS: Patients with NSCLC received atezolizumab 1-20 mg/kg or 1200 mg intravenously every 3 weeks. Baseline PD-L1 expression on tumour cells (TCs) and tumour-infiltrating immune cells (ICs) was assessed (VENTANA SP142 immunohistochemistry assay). Exploratory subgroup analyses investigated responses by baseline PD-L1 expression and oncogenic mutational status. RESULTS: Eighty-nine patients, 98% of whom had received previous systemic therapy, were evaluable for safety and antitumour activity. Atezolizumab was well tolerated, with grade III/IV treatment-related adverse events (TRAEs) observed in 10 patients (11%). All-grade TRAEs occurring in >10% of patients were fatigue, nausea and decreased appetite; grade III/IV TRAEs occurring in >2% of patients were fatigue, dyspnoea, hyponatremia and hypoxia. One patient died from treatment-unrelated pneumonia. Objective response rate (ORR) was 50% (95% confidence interval [CI], 28%-72%), 33% (20%-48%), 29% (18%-41%) and 11% (1%-35%) for the TC3 or IC3, TC2/3 or IC2/3, TC1/2/3 or IC1/2/3 and TC0 and IC0 subgroups, respectively. All-patient ORR was 23% (95% CI, 14%-33%). Median duration of response was 16.4 months (range, 7.2-53.4+). One-, 2-, and 3-year survival rates were 63% (95% CI, 53%-73%), 37% (26%-47%) and 28% (18%-38%), respectively. CONCLUSIONS: Single-agent atezolizumab was well tolerated with long-term clinical benefits, including durable responses and survival, in pretreated NSCLC. Improved responses and survival rates were seen with increasing baseline PD-L1 expression. CLINICALTRIALS. GOV IDENTIFIER: NCT01375842.

Atezolizumab (MPDL3280A) Monotherapy for Patients With Metastatic Urothelial Cancer: Long-term Outcomes From a Phase 1 Study.

IMPORTANCE: Atezolizumab (anti-programmed death ligand 1) has demonstrated safety and activity in advanced and metastatic urothelial carcinoma, but its long-term clinical profile remains unknown. OBJECTIVE: To report long-term clinical outcomes with atezolizumab therapy for patients with metastatic urothelial carcinoma. DESIGN, SETTING, AND PARTICIPANTS: Patients were enrolled in an expansion cohort of an ongoing, open-label, phase 1 study. Median follow-up was 37.8 months (range, >0.7 to 44.4 months). Enrollment occurred between March 2013 and August 2015 at US and European academic medical centers. Eligible patients had measurable disease per Response Evaluation Criteria in Solid Tumors version 1.1, Eastern Cooperative Oncology Group performance status 0 to 1, and a representative tumor sample. Programmed death ligand 1 expression on immune cells was assessed (VENTANA SP142 assay). INTERVENTIONS: Atezolizumab was given intravenously every 3 weeks until unacceptable toxic effects, protocol nonadherence, or loss of clinical benefit. MAIN OUTCOMES AND MEASURES: Primary outcome was safety. Secondary outcomes included objective response rate, duration of response, and progression-free survival. Response and overall survival were assessed in key baseline subgroups. RESULTS: Ninety-five patients were evaluable (72 [76%] male; median age, 66 years [range, 36-89 years]). Forty-five (47%) received atezolizumab as third-line therapy or greater. Nine patients (9%) had a grade 3 to 4 treatment-related adverse event, mostly within the first treatment year; no serious related adverse events were observed thereafter. One patient (1%) discontinued treatment due to a related event. No treatment-related deaths occurred. Responses occurred in 26% (95% CI, 18%-36%) of patients. Median duration of response was 22.1 months (range, 2.8 to >41.0 months), and median progression-free survival was 2.7 months (95% CI, 1.4-4.3 months). Median overall survival was 10.1 months (95% CI, 7.3-17.0 months); 3-year OS rate was 27% (95% CI, 17%-36%). Response occurred in 40% (95% CI, 26%-55%; n = 40) and 11% (95% CI, 4%-25%; n = 44) of patients with programmed death ligand 1 expression of at least 5% tumor-infiltrating immune cells (IC2/3) or less than 5% (IC0/1), respectively. Median overall survival in patients with IC2/3 and IC0/1 was 14.6 months (95% CI, 9.0 months to not estimable) and 7.6 months (95% CI, 4.7 to 13.9 months), respectively. CONCLUSIONS AND RELEVANCE: Atezolizumab remained well tolerated and provided durable clinical benefit to a heavily pretreated metastatic urothelial carcinoma population in this long-term study. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01375842.

PI3K orchestration of the in vivo persistence of chimeric antigen receptor-modified T cells.

In vivo persistence of chimeric antigen receptor (CAR)-modified T cells correlates with therapeutic efficacy, yet CAR-specific factors that support persistence are not well resolved. Using a CD33-specific CAR in an acute myeloid leukemia (AML) model, we show how CAR expression alters T cell differentiation in a ligand independent manner. Ex vivo expanded CAR-T cells demonstrated decreased naïve and stem memory populations and increased effector subsets relative to vector-transduced control cells. This was associated with reduced in vivo persistence. Decreased persistence was not due to specificity or tumor presence, but to pre-transfer tonic signaling through the CAR CD3ζ ITAMs. We identified activation of the PI3K pathway in CD33 CAR-T cells as responsible. Treatment with a PI3K inhibitor modulated the differentiation program of CAR-T cells, preserved a less differentiated state without affecting T cell expansion, and improved in vivo persistence and reduced tumor burden. These results resolve mechanisms by which tonic signaling of CAR-T cells modulates their fate, and identifies a novel pharmacologic approach to enhance the durability of CAR-T cells for immunotherapy.

Anti-CD33 chimeric antigen receptor targeting of acute myeloid leukemia.

Current therapies for acute myeloid leukemia are associated with high failure and relapse rates. Adoptive immunotherapies, which have shown promise in the treatment of hematologic malignancies, have the potential to target acute myeloid leukemia through pathways that are distinct and complementary to current approaches. Here, we describe the development of a novel adoptive immunotherapy specific for this disease. We generated a second generation CD33-specific chimeric antigen receptor capable of redirecting cytolytic effector T cells against leukemic cells. CD33 is expressed in approximately 90% of acute myeloid leukemia cases and has demonstrated utility as a target of therapeutic antibodies. Chimeric antigen receptor-modified T cells efficiently killed leukemia cell lines and primary tumor cells in vitro. The anti-leukemia effect was CD33-specific, mediated through T-cell effector functions, and displayed tumor lysis at effector:target ratios as low as 1:20. Furthermore, the CD33-redirected T cells were effective in vivo, preventing the development of leukemia after prophylactic administration and delaying the progression of established disease in mice. These data provide pre-clinical validation of the effectiveness of a second-generation anti-CD33 chimeric antigen receptor therapy for acute myeloid leukemia, and support its continued development as a clinical therapeutic.

Recent research and future prospects for gemtuzumab ozogamicin: could it make a comeback?

Gemtuzumab ozogamicin (GO), a humanized anti-CD33 monoclonal antibody conjugated to calicheamicin, was initially granted accelerated US FDA approval for the treatment of acute myeloid leukemia (AML), but was later voluntarily withdrawn from the market because of increased toxicity and lack of benefit in a Phase III clinical trial. However, subsequently published clinical trials that compared standard chemotherapy to chemotherapy plus GO in children and adults with AML demonstrated clinical benefit of GO in certain subgroups of patients, leading to renewed interest in GO. Although the re-emergence of GO into the clinic is uncertain, these results validate the use of CD33 as a target for AML therapy. Much research is underway to develop novel anti-CD33 therapeutics that may be able to pick up where GO left off.

Gemtuzumab ozogamicin can reduce minimal residual disease in patients with childhood acute myeloid leukemia.

BACKGROUND: Gemtuzumab ozogamicin (GO) is an active agent for the treatment of CD33-postive acute myeloid leukemia (AML) and may improve the outcome of specific patient subgroups when combined with conventional chemotherapy. However, to the best of the authors' knowledge, the effects of GO on levels of minimal residual disease (MRD) are unknown. METHODS: Pediatric patients with AML who received GO, either alone or in combination with chemotherapy on the AML02 multicenter trial, were analyzed to determine the effects of GO on MRD and outcome. RESULTS: Among 17 patients who received GO alone because of persistent leukemia, 14 had a reduction in their MRD level and 13 became MRD negative. Of the 29 who received chemotherapy in combination with GO after responding poorly to chemotherapy, 28 demonstrated reduced MRD and 13 became MRD negative. Treatment with GO effectively reduced MRD before hematopoietic stem cell transplantation and was not found to be associated with increased treatment-related mortality after transplantation. CONCLUSIONS: GO is effective in reducing MRD levels in pediatric patients with AML and may improve the outcome of those patients at high risk of disease recurrence.

Antibody buffering of systemically administered lysozyme.

OBJECTIVE: To assess the ability of an anti-lysozyme antibody to stabilize the plasma pharmacokinetics of lysozyme through a 'buffering' effect. METHODS: Hen egg lysozyme was radiolabeled with (14)C and infused with or without the murine anti-lysozyme antibody D1.3 into the jugular vein of rats. The dosages of antibody and lysozyme were varied, and the antibody and lysozyme were administered either together or in separate infusions. RESULTS: Buffering of lysozyme with an equimolar amount of D1.3 more than doubled the plasma half-life of lysozyme and addition of more antibody buffer prolonged the half-life to an even greater extent. D1.3 bound lysozyme that was infused several minutes after the D1.3 administration, indicating that D1.3 can be charged with drug in vivo. CONCLUSION: Antibody buffering of monovalent therapeutic enzymes is possible and may have potential for clinical use.

Antibody buffering in the brain.

The efficacy of chemotherapy on brain tumors is often hindered by the presence of the blood brain barrier. This barrier keeps many systemically administered substances from entering the cerebrospinal fluid (CSF), while allowing intrathecally administered drugs free passage out of that compartment. Therefore, achieving a therapeutic concentration of a cell cycle inhibitor in the CSF for a time long enough to have a cytotoxic effect on slow-growing tumor cells has proven difficult. The ability of an antibody to prolong ligand half-life and bioactivity has been previously described occurring in the plasma. This phenomenon has not yet been described or exploited for use in the CSF compartment. Antibodies often have a longer residence time in the CSF than small-molecule drugs, so antibody buffering, administration of a drug with its specific antibody, can prolong the bioactive lifetime of a drug in the CSF. Here we describe antibody buffering of the small molecule hapten 2-phenyl-oxazol-5-one-methylene-gamma-amino butyrate in the CSF of a rats. Not only does the presence of an antibody buffer increase the half-life of both total and free hapten in the CSF, but the antibody can be re-charged in situ with fresh hapten, even days after the initial antibody infusion. Antibody buffering may provide a viable option for delivering a stable, bio-available concentration of a drug that is normally rapidly eliminated from the CSF.