Stringent monitoring can decrease mortality of immune checkpoint inhibitor induced cardiotoxicity.

Background: Immune checkpoint inhibitor (ICI)-induced myocarditis is a rare immune-related adverse event (irAE) with a fatality rate of 40%-46%. However, irMyocarditis can be asymptomatic. Thus, improved monitoring, detection and therapy are needed. This study aims to generate knowledge on pathogenesis and assess outcomes in cancer centers with intensified patient management. Methods: Patients with cardiac irAEs from the SERIO registry (www.serio-registry.org) were analyzed for demographics, ICI-related information (type of ICI, therapy line, combination with other drugs, onset of irAE, and tumor response), examination results, irAE treatment and outcome, as well as oncological endpoints. Cardiac biopsies of irMyocarditis cases (n = 12) were analyzed by Nanostring and compared to healthy heart muscle (n = 5) and longitudinal blood sampling was performed for immunophenotyping of irMyocarditis-patients (n = 4 baseline and n = 8 during irAE) in comparison to patients without toxicity under ICI-therapy (n = 4 baseline and n = 7 during ICI-therapy) using flow cytometry. Results: A total of 51 patients with 53 cardiac irAEs induced by 4 different ICIs (anti-PD1, anti-PD-L1, anti-CTLA4) were included from 12 centers in 3 countries. Altogether, 83.0% of cardiac irAEs were graded as severe or life-threatening, and 11.3% were fatal (6/53). Thus, in centers with established consequent troponin monitoring, work-up upon the rise in troponin and consequent treatment of irMyocarditis with corticosteroids and -if required-second-line therapy mortality rate is much lower than previously reported. The median time to irMyocarditis was 36 days (range 4-1,074 days) after ICI initiation, whereas other cardiotoxicities, e.g. asystolia or myocardiopathy, occurred much later. The cytokine-mediated signaling pathway was differentially regulated in myocardial biopsies as compared to healthy heart based on enrichment Gene Ontology analysis. Additionally, longitudinal peripheral blood mononuclear cell (PBMC) samples from irMyocarditis-patients indicated ICI-driven enhanced CD4+ Treg cells and reduced CD4+ T cells. Immunophenotypes, particularly effector memory T cells of irMyocarditis-patients differed from those of ICI-treated patients without side effects. LAG3 expression on T cells and PD-L1 expression on dendritic cells could serve as predictive indicators for the development of irMyocarditis. Conclusion: Interestingly, our cohort shows a very low mortality rate of irMyocarditis-patients. Our data indicate so far unknown local and systemic immunological patterns in cardiotoxicity.

Second-line therapies for steroid-refractory immune-related adverse events in patients treated with immune checkpoint inhibitors.

BACKGROUND: Immune checkpoint inhibitors (ICI) induce adverse events (irAEs) that do not respond to steroids, i.e. steroid-refractory (sr) irAEs, and irAEs in which steroids cannot be tapered, i.e. steroid-dependent (sd) irAEs, in about 10% of cases. An evidence-based analysis of the effectiveness of second-line immunosuppressive agents with regard to irAE and tumor control is lacking. METHODS: The international web-based Side Effect Registry Immuno-Oncology (SERIO; http://serio-registry.org) is a collaborative initiative with the Paul-Ehrlich-Institute to document rare, severe, complex or therapy-refractory immunotherapy-induced side effects. The registry was queried on August 1, 2023 for cases of irAEs which were treated with second-line therapies. RESULTS: From a total of 1330 cases, 217 patients (16.3%) received 249 second-line therapies. A total of 19 different second-line therapies were employed, including TNF-alpha antagonists (46.5%), intravenous immunoglobulins (IVIG; 19.1%), mycophenolate mofetil (15.9%), and methotrexate (3.6%). Therapy choices were determined by the type of irAE. The time to onset of sr-/sd-irAEs after ICI initiation did not consistently differ from steroid-responsive irAEs. While 74.3% of sr-/sd-irAEs resolved and 13.1% had improved, 4.3% persisted, 3.9% resulted in permanent sequelae, and 4.3% in death with ongoing symptoms. Infliximab exhibited potential for earlier symptom improvement compared to mycophenolate mofetil or IVIG. Tumor response in patients with second-line treated sd-/sr-irAE was similar to patients with irAEs treated with steroids only. CONCLUSION: Several second-line therapies are effective against sr-/sd-irAEs, the second-line therapies show no clear negative impact on tumor response, and infliximab shows potential for faster improvement of symptoms. However, prospective comparative data are needed.

Extracorporeal Photopheresis as a Treatment Option for Immune-Related Adverse Events: Two Case Reports and a Prospective Study.

The wide use of immune checkpoint inhibitors has increased the frequency of immune-related adverse events (irAEs). While many are managed with corticosteroids or hormone substitution, up to 14.9% of irAEs are steroid-refractory or steroid-dependent and thus require second-line treatment. These should reduce irAE-related morbidity and mortality and induce a few side effects of their own while maintaining the antitumor response. There is little comparative data on second-line therapies for irAEs. Two cases of irAEs could not be sufficiently managed with corticosteroids and subsequently received treatment with extracorporeal photopheresis (ECP), including one patient with immune-related erosive oral lichen planus and one patient with immune-related colitis. In both cases, the irAE resolved with ECP in combination with immunosuppressive drugs, that is 4 weeks and 10 weeks after the start of ECP, respectively. To investigate this approach, a prospective clinical study that compares ECP and other second-line therapies for the treatment of steroid-refractory and steroid-dependent irAEs with regard to immunophenotype and therapy response has been designed. ECP could be a treatment option for steroid-refractory and steroid-dependent irAEs, given its good safety profile and lack of adverse effects on antitumor response. Comparative prospective studies are needed to generate an evidence base.

The side effect registry immuno-oncology (SERIO) - A tool for systematic analysis of immunotherapy-induced side effects.

BACKGROUND: Immunotherapies such as immune checkpoint inhibitors (ICI) are effective in multiple tumor entities but induce a plethora of side effects. Comprehensive real-world analyses are essential to identify new signals, characterize diagnostic features, enable risk assessment, determine pathomechanisms, assess effectiveness of side effect management and compare tumor outcomes. METHODS: The international online `Side-Effect Registry Immuno-Oncology´ (SERIO; www.serio-registry.org) collects rare, complex, and severe immunotherapy-induced side effects across all tumor entities with a strong focus on ICI-induced immune-related adverse events (irAE). The relational database management system (RDMS) contains structured data on patient and tumor characteristics, type of immunotherapy, treatment of side effects, and outcome of tumor and irAE. Data are captured within 25 organ modules including new modules for immune effector cell-associated neurotoxicity syndrome (ICANS) for CAR-T-cell therapies and cytokine release syndrome (CRS) for bispecific antibodies. Information on biological samples is gathered. RESULTS: A total of 1398 irAE cases have been documented by 58 centers from 13 countries in patients with 17 tumor types. IrAEs were induced by nine different immunotherapies including tebentafusp and CAR-T cell therapies, and resulted, among others, in neurological (7.6%), pulmonary (4.0%), and cardiac toxicities (2.9%). 50.0% of all irAEs were graded severe or life-threatening and 23.0% of patients received second-line therapy for steroid-refractory or steroid-dependent irAE. SERIO has contributed to 44 original publications on topics ranging from irMyocarditis to irEncephalitis to long-term persistent sequelae of immunotherapy. CONCLUSIONS: A reliable evidence base is crucial for decision-making in rare, complex or therapy-refractory irAE. SERIO can help optimize side effect management and thereby reduce morbidity and mortality induced by immunotherapy.

Tumor lysis syndrome induced by tebentafusp.

Tebentafusp, a bispecific T-cell receptor fusion protein directed against gp100 and CD3, can improve survival in patients with metastatic uveal melanoma and was recently approved for the treatment of HLA-A*02:01-positive uveal melanoma patients. Since tebentafusp often induces cytokine-release syndrome, doses must be escalated and patients monitored as inpatients after the first infusions. The occurrence of tumor lysis syndrome, a potentially life-threatening condition, after administration of a single dose of tebentafusp, is reported here. With adequate therapy, including the application of rasburicase, the patient made a full recovery. It is important to raise awareness of the adverse event profile of this new therapeutic approach among healthcare professionals to promptly recognize and treat side effects.

Tebentafusp is a new treatment for a type of eye cancer called uveal melanoma. It helps the body's defense system fight against cancer cells and has shown promise in helping patients live longer. However, not all patients with uveal melanoma can use this treatment. Only those who have a specific gene marker called HLA-A*02:01-positive can benefit from it. Like any new treatment, tebentafusp may have some side effects. One of them is called cytokine-release syndrome, which can cause symptoms like rash, fever and flu-like feelings. Usually, this side effect is not serious and can be treated well. There was a rare but serious case where one patient had a bad reaction after getting only one dose of tebentafusp. This reaction is called tumor lysis syndrome, which happens when cancer cells break down quickly and release harmful substances into the blood. This can be life-threatening. Thankfully, the patient received the right treatment and got better. This information is shared here with doctors and patients, so they know about possible side effects and can use tebentafusp safely.

Tebentafusp in Patients with Metastatic Uveal Melanoma: A Real-Life Retrospective Multicenter Study.

BACKGROUND: Tebentafusp has recently been approved for the treatment of metastatic uveal melanoma (mUM) after proving to have survival benefits in a first-line setting. PATIENTS AND METHODS: This retrospective, multicenter study analyzed the outcomes and safety of tebentafusp therapy in 78 patients with mUM. RESULTS: Patients treated with tebentafusp had a median PFS of 3 months (95% CI 2.7 to 3.3) and a median OS of 22 months (95% CI 10.6 to 33.4). In contrast to a published Phase 3 study, our cohort had a higher rate of patients with elevated LDH (65.4% vs. 35.7%) and included patients with prior systemic and local ablative therapies. In patients treated with tebentafusp following ICI, there was a trend for a longer median OS (28 months, 95% CI 26.9 to 29.1) compared to the inverse treatment sequence (24 months, 95% CI 13.0 to 35.0, p = 0.257). The most common treatment-related adverse events were cytokine release syndrome in 71.2% and skin toxicity in 53.8% of patients. Tumor lysis syndrome occurred in one patient. CONCLUSIONS: Data from this real-life cohort showed a median PFS/OS similar to published Phase 3 trial data. Treatment with ICI followed by tebentafusp may result in longer PFS/OS compared to the inverse treatment sequence.

Steroid-Refractory Immune-Related Adverse Events Induced by Checkpoint Inhibitors.

The occurrence, second-line management and outcome of sr/sd-irAEs was investigated in patients with skin cancer. All skin cancer patients treated with immune checkpoint inhibitors (ICIs) between 2013 and 2021 at a tertiary care center were analyzed retrospectively. Adverse events were coded by CTCAE version 5.0. The course and frequency of irAEs were summarized using descriptive statistics. A total of 406 patients were included in the study. In 44.6% (n = 181) of patients, 229 irAEs were documented. Out of those, 146 irAEs (63.8%) were treated with systemic steroids. Sr-irAEs and sd-irAEs (n = 25) were detected in 10.9% of all irAEs, and in 6.2% of ICI-treated patients. In this cohort, infliximab (48%) and mycophenolate mofetil (28%) were most often administered as second-line immunosuppressants. The type of irAE was the most important factor associated with the choice of second-line immunosuppression. The Sd/sr-irAEs resolved in 60% of cases, had permanent sequelae in 28% of cases, and required third-line therapy in 12%. None of the irAEs were fatal. Although these side effects manifest in only 6.2% of patients under ICI therapy, they impose difficult therapy decisions, especially since there are few data to determine the optimal second-line immunosuppression.

Health-related quality of life (EuroQol 5D-5L) in patients with autoimmunity in the context of immunotherapy: A large dataset comprising cancer patients after cessation of checkpoint inhibitor therapy and patients with autoimmune diseases.

This dataset contains demographic, clinical, and health-related quality of life (HRQoL) data from 2905 patients including 200 cancer patients after immune checkpoint inhibitor (ICI) cessation and 2705 patients with a wide variety of autoimmune diseases. Within this multicenter, cross-sectional survey study data were collected questionnaire-based in cancer patients (ICI-patients) ≥ 18 years of age who had received at least one dose of ICI with ≥ 12 weeks since ICI discontinuation. Patients with autoimmune diseases (AI-patients) were ≥ 18 years, had at least one autoimmune disease and had never received ICI. ICI-patients were recruited in three skin cancer centers and via support groups. AI-patients were recruited in an outpatient clinic for internal medicine and via support groups. Specific questionnaires for ICI-patients/AI-patients were provided paper-based for patients from outpatient clinics and online for patients from support groups. Both questionnaires contained sections with demographic information, clinical data, and the standardized patient-reported outcome measure EuroQol 5D-5L (EQ-5D-5L) to assess HRQoL. Clinical data focused on autoimmunity and therapy of autoimmunity in (1) ICI-patients referring to particularly persistent immune-related adverse events (persistent irAEs) and in (2) AI-patients referring to respective autoimmune diseases. Additionally, specific items on cancer and cancer therapy were included in ICI-patients, and AI-patients were asked about the presence of acute exacerbations of autoimmune diseases. This dataset contains the raw data for ICI-patients and AI-patients, analyzed data on patient demographics, clinical characteristics and HRQoL scores among ICI-patients with/without persistent irAEs and among AI-patients. The data provide a basis for further investigations within the cohort of ICI-patients after ICI cessation and/or for AI-patients with different autoimmune diseases with regard to HRQoL, autoimmunity and therapy of autoimmunity.

Cost-effectiveness of Response-Adapted De-escalation of Immunotherapy in Advanced Melanoma.

Importance: Combination immunotherapy with nivolumab and ipilimumab has markedly improved outcomes for patients with advanced melanoma. However, these therapies pose a considerable financial burden to both patients and the health care system. The ADAPT-IT trial demonstrated comparable progression-free and overall survival for patients with response-adapted ipilimumab discontinuation compared with standard of care (SOC). Objective: To determine the cost-effectiveness of ipilimumab discontinuation for patients with interim imaging-confirmed tumor response in the treatment of advanced melanoma. Design, Setting, and Participants: This cost-effectiveness analysis was performed using data from the ADAPT-IT (follow-up of 33 months) and CheckMate 067 (follow-up of 6.5 years) trials, as well as published literature over the ADAPT-IT trial duration of 33 months. The analysis was performed in a US setting from a US-payer perspective, and the willingness-to-pay (WTP) threshold was set at $100 000/quality-adjusted life-year (QALY). A total of 355 patients with previously untreated melanoma (unresectable stage III or IV metastatic melanoma) were included. Exposure: Response-adapted ipilimumab discontinuation compared with SOC therapy. Main Outcomes and Measures: The primary outcomes of the CheckMate trial were overall survival and progression-free survival, while that of ADAPT-IT was objective response. This informed a decision model to estimate lifetime costs and QALYs associated with both strategies. Incremental cost, effectiveness, and cost-effectiveness ratio were assessed. Sensitivity and scenario analyses were performed to account for variability in trials and input parameters. Results: Of the 355 patients included in the analysis, 41 patients were from the ADAPT-IT trial (median age, 65 years; 28 [68%] male) and 314 patients from the CheckMate 067 trial (median age, 61 years; 206 [66%] male). Response-adapted treatment was the cost-effective option in 94.0% of scenarios based on Monte Carlo simulations, with a dominant incremental cost-effectiveness ratio and an incremental net monetary benefit of $28 849 compared with SOC therapy. Cost savings were estimated at $19 891 per patient compared with SOC. In scenario analyses, current SOC was only considered as a cost-effective option under best survival assumptions and if the willingness-to-pay threshold exceeded $630 000/QALY. Conclusions and Relevance: This economic evaluation demonstrated that response-adapted treatment de-escalation in patients with advanced melanoma may lead to considerable savings in health care costs and could represent the most cost-effective strategy across various resource settings. Future trials should aim to provide further evidence on noninferiority.

Persistent immune-related adverse events after cessation of checkpoint inhibitor therapy: Prevalence and impact on patients' health-related quality of life.

BACKGROUND: Immune checkpoint inhibitors (ICIs) may induce persistent immune-related adverse events (irAEs). We investigated persistent irAEs and implications on patients' lives compared to non-ICI-induced autoimmune diseases (AIs). METHODS: The multicentre, cross-sectional study comprised 200 patients with cancer ≥12 weeks after ICI cessation (ICI-patients) and 2705 patients with AIs (AI-patients), recruited in German outpatient clinics and support groups. The prevalence of persistent irAEs subdivided in long-term (12 weeks to <12 months) and chronic irAEs (≥12 months) since ICI discontinuation, health-related quality of life (HRQoL) using the EuroQol 5D-5L (EQ-Index/VAS score), and burden of autoimmune symptoms and respective therapies were assessed. RESULTS: Long-term/chronic irAEs occurred in 51.9%/35.5% of outpatient ICI-patients, including arthralgia (16.7%/16.1%), myalgia (13.0%/14.0%), hypothyroidism (11.1%/10.8%), xerostomia (7.4%/8.6%), vitiligo (13.0%/7.5%) and hypophysitis (9.3%/7.5%). ICI-patients with long-term/chronic irAEs reported clinically significantly reduced HRQoL compared to ICI-patients without long-term/chronic irAEs (EQ-Index score: 0.767/0.752 versus 0.920/0.923, p < 0.001/0.001; EQ-VAS score: 52.2/52.0 versus 63.6/74.7, p =/< 0.040/0.001). Multiple linear regression analyses confirmed clinically significant reductions in HRQoL scores by chronic irAEs (EQ-Index/VAS score: -0.163/-23.4, p < 0.001/0.001). HRQoL, burden of autoimmune symptoms and burden of respective therapies in ICI-patients with chronic irAEs were similar to AI-patients with non-exacerbated AIs. Patients with chronic irAEs felt inadequately informed about side-effects compared to patients without chronic irAEs (p < 0.001). CONCLUSION: Persistent irAEs impose a significant burden on patients after ICI cessation. Especially in early tumour stages, risk-benefit ratios must be carefully evaluated, and patients need to be informed about potential long-term sequelae.

Development of Lymphopenia during Therapy with Immune Checkpoint Inhibitors Is Associated with Poor Outcome in Metastatic Cutaneous Melanoma.

Predictive markers for immune checkpoint inhibitor (ICI) therapy are needed. Thus, baseline blood counts have been investigated as biomarkers, showing that lymphopenia at the start of therapy with (ICI) is associated with a worse outcome in metastatic melanoma. We investigated the relationship between the occurrence of lymphopenia under ICI and disease outcome. Patients with metastatic melanoma who had undergone therapy with ICI were identified in our database. Only patients with a normal lymphocyte count at baseline were included in this retrospective study. Progression-free survival (PFS) and overall survival (OS) were compared between patients in which lymphopenia occurred during ICI therapy and those who did not develop lymphopenia. In total, 116 patients were analyzed. Lymphopenia occurred in 42.2% of patients, with a mean onset after 17 weeks (range 1-180 weeks). The occurrence of lymphopenia during immunotherapy was significantly associated with a shorter PFS and OS. Patients who developed lymphopenia (n = 49) had a mean PFS of 13.3 months (range 1-67 months) compared to 16.9 months (range 1-73 months) for patients who did not develop lymphopenia (n = 67; p = 0.025). Similarly, patients with lymphopenia had a significantly shorter OS of 28.1 months (range 2-70 months) compared with 36.8 months (range 4-106 months) in patients who did not develop lymphopenia (p = 0.01). Patients with metastatic melanoma who develop lymphopenia during ICI therapy have a worse prognosis with significantly shorter PFS and OS compared with patients who do not develop lymphopenia.

Checkpoint-inhibitor induced Polyserositis with Edema.

BACKGROUND: As immune checkpoint inhibitors (ICI) are increasingly being used due to effectiveness in various tumor entities, rare side effects occur more frequently. Pericardial effusion has been reported in patients with advanced non-small cell lung cancer (NSCLC) after or under treatment with immune checkpoint inhibitors. However, knowledge about serositis and edemas induced by checkpoint inhibitors in other tumor entities is scarce. METHODS AND RESULTS: Four cases with sudden onset of checkpoint inhibitor induced serositis (irSerositis) are presented including one patient with metastatic cervical cancer, two with metastatic melanoma and one with non-small cell lung cancer (NSCLC). In all cases treatment with steroids was successful in the beginning, but did not lead to complete recovery of the patients. All patients required multiple punctures. Three of the patients presented with additional peripheral edema; in one patient only the lower extremities were affected, whereas the entire body, even face and eyelids were involved in the other patients. In all patients serositis was accompanied by other immune-related adverse events (irAEs). CONCLUSION: ICI-induced serositis and effusions are complex to diagnose and treat and might be underdiagnosed. For differentiation from malignant serositis pathology of the punctured fluid can be helpful (lymphocytes vs. malignant cells). Identifying irSerositis as early as possible is essential since steroids can improve symptoms.

Skin manifestations reported in association with COVID-19 infection.

The prevalence of all cutaneous manifestations directly associated with COVID-19 infection is unknown, but the number of reports is rapidly increasing and provisional knowledge is rapidly evolving. Skin manifestations reported can be classified into (1) manifestations unspecifically indicating possible infectious diseases, i.e. maculopapular exanthem, urticaria and erythema multiforme, and (2) manifestations more specifically indicating COVID-19 infection, i.e. varicella-like, livedo reticularis or chilblain-like eruptions. The latter appear to be associated with thrombovascular events and vascular pathologies.

Cofactors of wheat-dependent exercise-induced anaphylaxis do not increase highly individual gliadin absorption in healthy volunteers.

BACKGROUND: In wheat-dependent exercise-induced anaphylaxis (WDEIA), cofactors such as exercise, acetylsalicylic acid (ASA), alcohol or unfavorable climatic conditions are required to elicit a reaction to wheat products. The mechanism of action of these cofactors is unknown, but an increase of gliadin absorption has been speculated. Our objectives were to study gliadin absorption with and without cofactors and to correlate plasma gliadin levels with factors influencing protein absorption in healthy volunteers. METHODS: Twelve healthy probands (six males, six females; aged 20-56 years) ingested 32 g of gluten without any cofactor or in combination with cofactors aerobic and anaerobic exercise, ASA, alcohol and pantoprazole. Gliadin serum levels were measured up to 120 min afterwards and the intestinal barrier function protein zonulin in stool was collected before and after the procedure; both were measured by ELISA. Stool microbiota profile was obtained by 16S gene sequencing. RESULTS: Within 15 min after gluten intake, gliadin concentrations in blood serum increased from baseline in all subjects reaching highly variable peak levels after 15-90 min. Addition of cofactors did not lead to substantially higher gliadin levels, although variability of levels was higher with differences between individuals (p < 0.001) and increased levels at later time points. Zonulin levels in stool were associated neither with addition of cofactors nor with peak gliadin concentrations. There were no differences in gut microbiota between the different interventions, although the composition of microbiota (p < 0.001) and the redundancy discriminant analysis (p < 0.007) differed in probands with low versus high stool zonulin levels. CONCLUSION: The adsorption of gliadin in the gut in healthy volunteers is less dependent on cofactors than has been hypothesized. Patients with WDEIA may have a predisposition needed for the additional effect of cofactors, e.g., hyperresponsive or damaged intestinal epithelium. Alternatively, other mechanisms, such as cofactor-induced blood flow redistribution, increased activity of tissue transglutaminase, or increases in plasma osmolality and acidosis inducing basophil and mast cell histamine release may play the major role in WDEIA.

Digital ulcers score: a scoring system to assess digital ulcers in patients suffering from systemic sclerosis.

OBJECTIVES: To develop a standardized scoring system to assess the severity of DUs in SSc patients and correlate it with functional outcomes. METHODS: In this cross-sectional, longitudinal study in SSc patients with DUs (n=65) we developed a digital ulcers score (DUS) for the assessment of DUs. DUS and the ABILHAND score were measured at each visit and differences were analysed using Tamhane's T2 test. Spearman's Rho test was applied for correlational analysis of DUS and functional outcomes. We calculated a linear regression model using clustered standard errors for correlation analysis between DUS and ABILHAND over time. RESULTS: 117 assessments of DUS were performed in 65 SSc patients. Mean DUS was 11.6±1.9 (range: 0-68). Subgroup analyses showed a higher DUS in patients suffering from diffuse cutaneous SSc when compared to patients with limited cutaneous SSc (12.8±3.0 vs. 9.7±2.2 p=0.18). There was no correlation between the DUS and manual ability using the ABILHAND score (overall: n=106 r=-0.138, p=0.22). We observed a small but significant linear correlation between the DUS and the ABILHAND score for a single patient over time (n=14, R2=0.31, r=0.06, p=0.02). CONCLUSIONS: The DUS is a feasible scoring instrument to assess severity of DUs in SSc patients. In accordance with the literature the severity of DUs correlates with clinical parameters but also severity of the disease. Further study is needed to establish the DUS as a standardized tool for the assessment of DUs.

Patient-individualized CD8⁺ cytolytic T-cell therapy effectively combats minimal residual leukemia in immunodeficient mice.

Adoptive transfer of donor-derived cytolytic T-lymphocytes (CTL) has evolved as a promising strategy to improve graft-versus-leukemia (GvL) effects in allogeneic hematopoietic stem-cell transplantation. However, durable clinical responses are often hampered by limited capability of transferred T cells to establish effective and sustained antitumor immunity in vivo. We therefore analyzed GvL responses of acute myeloid leukemia (AML)-reactive CD8(+) CTL with central and effector memory phenotype in a new allogeneic donor-patient specific humanized mouse model. CTL lines and clones obtained upon stimulation of naive CD45RA(+) donor CD8(+) T cells with either single HLA antigen-mismatched or HLA-matched primary AML blasts, respectively, elicited strong leukemia reactivity during cytokine-optimized short to intermediate (i.e., 2-8 weeks) culture periods. Single doses of CTL were intravenously infused into NOD/scidIL2Rcg(null) mice when engraftment with patient AML reached bone marrow infiltration of 1-5%, clinically defining minimal residual disease status. This treatment resulted in complete regression of HLA-mismatched and strong reduction of HLA-matched AML infiltration, respectively. Most importantly, mice receiving AML-reactive CTL showed significantly prolonged survival. Transferred CTL were detectable in murine bone marrow and spleen and demonstrated sustained AML-reactivity ex vivo. Moreover, injections with human IL-15 clearly promoted CTL persistence. In summary, we show that naive donor-derived CD8(+) CTL effectively combat patient AML blasts in immunodeficient mice. The donor-patient specific humanized mouse model appears suitable to evaluate therapeutic efficacy of AML-reactive CTL before adoptive transfer into patients. It may further help to identify powerful leukemia rejection antigens and T-cell receptors for redirecting immunity to leukemias even in a patient-individualized manner.