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B Conclusions: b Early ibrutinib-treatment of patients with asymptomatic Binet stage A CLL at high risk of progression failed to demonstrate an overall survival benefit when compared to placebo. B Introduction: b We present the final analysis of the phase 3, double-blind, placebo-controlled CLL12 trial evaluating ibrutinib in patients with early stage CLL at increased risk of progression defined by a comprehensive score (NCT02863718). [Extracted from the article]

B Introduction: b BTK-inhibitors have revolutionized treatment of CLL. Hoffmann-La Roche Ltd., Gilead, Janssen, Adapative Biotechnologies, Hexal Research funding: Abbvie, Beigene, AstraZeneca, Fa. Hoffmann-La Roche Ltd., Gilead, Janssen Educational grants: Abbvie, Beigene, AstraZeneca, Novartis, Celgene, Fa. [Extracted from the article]

Long-term data of chronic lymphocytic leukemia (CLL) patients with favorable risk who were treated with fludarabine, cyclophosphamide, and rituximab (FCR) within clinical trials show good efficacy. We here report long-term data collected within the GCLLSG registry. Altogether, 417 CLL patients who received first-line treatment with FCR were analyzed, of which 293 (70.3%) were treated outside of clinical trials. The median observation time from first-line was 95.8 (interquartile range 58.7-126.8) months. Focusing on data of 194 (46.5%) patients who received FCR first-line treatment after 2013 (start of data collection within GCLLSG registry), responses were documented in 85% of the patients, non-responses in 15%, and for 3.6% the assessment was missing. Median event-free survival (EFS, time until disease progression, subsequent treatment, or death) was 60.2 months with a 5-year EFS-rate of 50.6%. Patients with higher-risk disease, characterized by unmutated IGHV (N = 78), had a median EFS of 45.4 months with a 5-year EFS rate of 36.3%, while the median EFS was 77.5 months with a 5-year EFS rate of 60.3% in patients with mutated IGHV (N = 40). Median overall survival was not reached with a 5-year survival rate of 92.7%. In summary, first-line FCR was associated with long EFS, especially in patients exhibiting a mutated IGHV status., (© 2024 The Authors. European Journal of Haematology published by John Wiley & Sons Ltd.)

In patients with chronic lymphocytic leukemia, Richter transformation (RT) reflects the development of an aggressive lymphoma that is associated with poor response to chemotherapy and short survival. We initiated an international, investigator-initiated, prospective, open-label phase 2 study in which patients with RT received a combination of the PD-1 inhibitor tislelizumab plus the BTK inhibitor zanubrutinib for 12 cycles. Patients responding to treatment underwent maintenance treatment with both agents. The primary end point was overall response rate after six cycles. Of 59 enrolled patients, 48 patients received at least two cycles of treatment and comprised the analysis population according to the study protocol. The median observation time was 13.9 months, the median age was 67 (range 45-82) years. Ten patients (20.8%) had received previous RT-directed therapy. In total, 28 out of 48 patients responded to induction therapy with an overall response rate of 58.3% (95% confidence interval (CI) 43.2-72.4), including 9 (18.8%) complete reponse and 19 (39.6%) partial response, meeting the study's primary end point by rejecting the predefined null hypothesis of 40% (P = 0.008). Secondary end points included duration of response, progression-free survival and overall survival. The median duration of response was not reached, the median progression-free survival was 10.0 months (95% CI 3.8-16.3). Median overall survival was not reached with a 12-month overall survival rate of 74.7% (95% CI 58.4-91.0). The most common adverse events were infections (18.0%), gastrointestinal disorders (13.0%) and hematological toxicities (11.4%). These data suggest that combined checkpoint and BTK inhibition by tislelizumab plus zanubrutinib is an effective and well-tolerated treatment strategy for patients with RT. ClinicalTrials.gov Identifier: NCT04271956 ., (© 2023. The Author(s).)

Complex karyotypes have been associated with inferior outcomes in chronic lymphocytic leukemia (CLL) treated with chemoimmunotherapy (CIT), whereas their prognostic impact in the context of venetoclax-based treatments is still debated. In this prospective analysis on karyotype complexity in CLL, we evaluated the impact of complex (≥3 chromosomal aberrations [CAs], CKTs) and highly complex karyotypes (≥5 CAs; hCKTs) as well as specific aberrations in previously untreated patients without TP53 aberrations undergoing either CIT or time-limited venetoclax-based therapies in the phase 3 GAIA/CLL13 trial. Karyotype analyses were available for 895 of 926 patients (96.7%), of whom 153 (17%) had a CKT and 43 (5%) hCKT. In the CIT arm, CKT was associated with shorter progression-free survival (PFS) (hazard ratio [HR] 2.58; 95% confidence interval [95% CI], 1.54-4.32; P < .001) and overall survival (HR, 3.25; 95% CI, 1.03-10.26; P = .044). In the pooled venetoclax arms, a multivariable analysis identified hCKTs (HR, 1.96; 95% CI, 1.03-3.72; P = .041), but not CKTs, as independent adverse prognosticators for PFS. The presence of translocations (unbalanced and/or balanced) was also independently associated with shorter PFSs in the venetoclax arms. CIT led to the acquisition of additional CAs (mean CAs, 2.0-3.4; from baseline to CLL progression), whereas karyotype complexity remained stable after venetoclax-based treatments (2.0, both time points). This analysis establishes highly complex karyotypes and translocations as adverse prognostic factors in the context of venetoclax-based combination treatments. The findings of this study support the incorporation of karyotyping into the standard diagnostic workup of CLL, because it identifies patients at high risk of poor treatment outcomes and thereby improves prognostication. This trial was registered at www.clinicaltrials.gov as #NCT02950051., (© 2023 by The American Society of Hematology.)

UNFOLDER (Unfavorable Young Low-Risk Densification of R-Chemo Regimens) is an international phase-3 trial in patients 18-60 years with aggressive B-cell lymphoma and intermediate prognosis defined by age-adjusted International Prognostic Index (aaIPI) of 0 and bulky disease (≥7.5 cm) or aaIPI of 1. In a 2 × 2 factorial design patients were randomized to 6× R-CHOP-14 or 6× R-CHOP-21 (rituximab, cyclophosphamide, doxorubicin, vincristine, and prediso[lo]ne) and to consolidation radiotherapy to extralymphatic and bulky disease or observation. Response was assessed according to the standardized response criteria published in 1999, not including F-18 fluordesoxyglucose positron emission tomography/computed tomography (FDG-PET). Primary endpoint was event-free survival (EFS). A total of 695 of 700 patients were eligible for the intention-to-treat analysis. Totally 467 patients qualified for radiotherapy of whom 305 patients were randomized to receive radiotherapy (R-CHOP-21: 155; R-CHOP-14: 150) and 162 to observation (R-CHOP-21: 81, R-CHOP-14: 81). Two hundred twenty-eight patients not qualifying for radiotherapy were randomized for R-CHOP-14 versus R-CHOP-21. After a median observation of 66 months 3-year EFS was superior in the radiotherapy-arm versus observation-arm (84% versus 68%; P = 0.0012), due to a lower rate of partial responses (PR) (2% versus 11%). PR often triggered additional treatment, mostly radiotherapy. No significant difference was observed in progression-free survival (PFS) (89% versus 81%; P = 0.22) and overall survival (OS) (93% versus 93%; P = 0.51). Comparing R-CHOP-14 and R-CHOP-21 EFS, PFS and OS were not different. Patients randomized to radiotherapy had a superior EFS, largely due to a lower PR rate requiring less additional treatment (NCT00278408, EUDRACT 2005-005218-19)., Competing Interests: L. Thurner has received travel grants from Abbvie, Janssen and EUSA-Pharm, and has indicated consultancy for Takeda, Astra-Zeneca, Merck, EUSA-pharm. DK-M has received personal fees from Novartis, Astra-Zeneca, Gilead Sciences, GlaxoSmithKline, Janssen-Cilag, and nonfinancial support from Gilead Sciences, Janssen-Cilag, Takeda, Novartis. AV has received honoraria from Roche, Amgen, Kite, Gilead, Novartis, Bristol-Myers Squibb and has indicated a membership of the advisory board of Roche, Amgen, Kite, Gilead, Novartis, Bristol-Myers Squibb. UBK has received honoraria and advisory fees from Roche, Janssen-Cilag, Takeda, Bristol-Myers Squibb, Gilead, Hexal, Pfizer, Astra- Zeneca, Pentixapharm, Amgen, Novartis, MSD and has received clinical study support for Celgene, Takeda, BMS, Roche, Astra-Zeneca, Novartis, MSD, Janssen-Cilag, Pfizer. MN has received travel grants from Roche, Celgene and MSD and personal fees from Roche, Celgene, MSD, Janssen, Amgen, Incyte and Abbvie. FG participates in advisory board of Roche, Boehringer Ingelheim, Abbvie, Merck, Takeda, MSD, Sanofi, Pfizer, Novartis, Amgen and Janssen. RT has received grants from Atara and Roche and travel support from Roche, Atara, Celgene, Janssen and Abbvie; he has indicated a membership of the advisory board of Atara and Abbvie and has indicated consultancy for s Atara. PdNB has indicated consultancy for Roche, Incyte and Novartis. FM has received travel grants from Roche, Takeda, Janssen and Gilead and has indicated consultancy and advisory role for Roche, Gilead, Janssen, MSD, Takeda and Novartis. SS has received grants from Abbvie, Astra-Zeneca, Celgene, Gilead, Roche, Janssen, Novartis, Morphosys and has indicated consultancy for for Abbvie, Astra-Zeneca, Celgene, Gilead, Roche, Janssen, Novartis, Morphosys; he has received drug/equipment supplied by entity from Abbvie, Astra-Zeneca, Celgene, Gilead, Roche, Janssen, Novartis, Morphosys. VP has received grants from Deutsche Krebshilfe (German Cancer Aid), Chugai, Abbvie, Amgen, Roche and Bristol Myers Squibb. GH has received grants from Roche and Bristol Myers Squibb and personal fees from Bristol Myers Squibb, Roche, Amgen, Spectrum and MSD. All the other authors have no conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the European Hematology Association.)

Background: Randomized trials of venetoclax plus anti-CD20 antibodies as first-line treatment in fit patients (i.e., those with a low burden of coexisting conditions) with advanced chronic lymphocytic leukemia (CLL) have been lacking., Methods: In a phase 3, open-label trial, we randomly assigned, in a 1:1:1:1 ratio, fit patients with CLL who did not have TP53 aberrations to receive six cycles of chemoimmunotherapy (fludarabine-cyclophosphamide-rituximab or bendamustine-rituximab) or 12 cycles of venetoclax-rituximab, venetoclax-obinutuzumab, or venetoclax-obinutuzumab-ibrutinib. Ibrutinib was discontinued after two consecutive measurements of undetectable minimal residual disease or could be extended. The primary end points were undetectable minimal residual disease (sensitivity, <10 -4 [i.e., <1 CLL cell in 10,000 leukocytes]) as assessed by flow cytometry in peripheral blood at month 15 and progression-free survival., Results: A total of 926 patients were assigned to one of the four treatment regimens (229 to chemoimmunotherapy, 237 to venetoclax-rituximab, 229 to venetoclax-obinutuzumab, and 231 to venetoclax-obinutuzumab-ibrutinib). At month 15, the percentage of patients with undetectable minimal residual disease was significantly higher in the venetoclax-obinutuzumab group (86.5%; 97.5% confidence interval [CI], 80.6 to 91.1) and the venetoclax-obinutuzumab-ibrutinib group (92.2%; 97.5% CI, 87.3 to 95.7) than in the chemoimmunotherapy group (52.0%; 97.5% CI, 44.4 to 59.5; P<0.001 for both comparisons), but it was not significantly higher in the venetoclax-rituximab group (57.0%; 97.5% CI, 49.5 to 64.2; P = 0.32). Three-year progression-free survival was 90.5% in the venetoclax-obinutuzumab-ibrutinib group and 75.5% in the chemoimmunotherapy group (hazard ratio for disease progression or death, 0.32; 97.5% CI, 0.19 to 0.54; P<0.001). Progression-free survival at 3 years was also higher with venetoclax-obinutuzumab (87.7%; hazard ratio for disease progression or death, 0.42; 97.5% CI, 0.26 to 0.68; P<0.001), but not with venetoclax-rituximab (80.8%; hazard ratio, 0.79; 97.5% CI, 0.53 to 1.18; P = 0.18). Grade 3 and grade 4 infections were more common with chemoimmunotherapy (18.5%) and venetoclax-obinutuzumab-ibrutinib (21.2%) than with venetoclax-rituximab (10.5%) or venetoclax-obinutuzumab (13.2%)., Conclusions: Venetoclax-obinutuzumab with or without ibrutinib was superior to chemoimmunotherapy as first-line treatment in fit patients with CLL. (Funded by AbbVie and others; GAIA-CLL13 ClinicalTrials.gov number, NCT02950051; EudraCT number, 2015-004936-36.)., (Copyright © 2023 Massachusetts Medical Society.)

Observation is the current standard of care for patients with early-stage asymptomatic chronic lymphocytic leukemia (CLL), as chemotherapy-based interventions have failed to prolong survival. We hypothesized that early intervention with ibrutinib would be well tolerated and lead to superior disease control in a subgroup of early-stage patients with CLL. The phase 3, double-blind, placebo-controlled CLL12 trial randomly assigned asymptomatic, treatment-naïve Binet stage A CLL patients at increased risk of progression in a 1:1 ratio to receive ibrutinib (n = 182) or placebo (n = 181) at a dose of 420 mg daily. At a median follow-up of 31 months, the study met its primary endpoint by significantly improving event-free survival in the ibrutinib group (median, not reached vs 47.8 months; hazard ratio = 0.25; 95% confidence interval = 0.14-0.43, P < .0001). Compared with placebo, ibrutinib did not increase overall toxicity, yielding similar incidence and severity of adverse events (AEs). The most common serious AEs were atrial fibrillation, pneumonia, and rash in the ibrutinib group, and basal cell carcinoma, pneumonia, and myocardial infarction in the placebo group. Ibrutinib-associated risk for bleeding (33.5%) was decreased by prohibiting the use of oral anticoagulants through an amendment of the study protocol and by avoiding CYP3A4 drug-drug interactions. Ibrutinib confirms efficacy in CLL patients at an early stage with an increased risk of progression. However, the results do not justify changing the current standard of "watch and wait." This trial was registered at www.clinicaltrials.gov as #NCT02863718., (© 2022 by The American Society of Hematology.)

Background: Lung cancer is a leading cause of cancer-related death in Germany and worldwide. Non-small cell lung cancer (NSCLC) comprises ~80% of lung cancer diagnoses; in White patients, around 10% of NSCLC cases are epidermal growth factor receptor mutation-positive ( EGFR m+). Head-to-head clinical trials have demonstrated superior efficacy with second-/third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) versus first-generation EGFR TKIs in EGFR m+ NSCLC. Data from routine clinical practice are necessary to confirm that clinical trial findings are transferable to real-world populations., Methods: In NCT02047903, a prospective non-interventional study in Germany, patients with EGFR m+ NSCLC received first-line afatinib until disease progression or intolerable adverse events. Key objectives were progression-free survival (PFS) rate at 12 months, objective response rate (ORR) and overall survival (OS). Safety/tolerability was also assessed., Results: Of 152 patients, 106 (69.7%) were female, 20 (13.1%) patients had an uncommon EGFR mutation and 51 patients (33.6%) had brain metastases. A starting dose of <40 mg was received by 39 (25.7%) patients. Overall, the 12-month PFS rate was 50.2% while the median PFS was 12.2 months. The ORR was 74.6% and the median OS was 30.4 months. In patients with brain metastases and uncommon mutations, the median PFS was 10.5 and 10.7 months, and the ORR was 77.3% and 83.3%, respectively. Treatment effectiveness was similar in patients with a starting dose of <40 mg (median PFS: 16.4 months; ORR, 81.3%) and a starting dose of 40 mg (median PFS: 10.8 months; ORR, 72.1%). Adverse drug reactions were manageable and consistent with the known afatinib safety profile., Conclusion: The results support clinical trial data for afatinib in routine clinical practice, including in patients generally excluded from clinical trials. Outcomes were positive in patients with uncommon EGFR mutations and in those with brain metastases. Treatment benefit was also seen in patients receiving a <40 mg afatinib starting dose, supporting patient-tailored dosing., Competing Interests: Conflict of interest statement: This study was supported by Boehringer Ingelheim. Wolfgang Brückl has received honoraria for consulting from AstraZeneca, BMS, Boehringer Ingelheim, Celgene, Chugai, Lilly, MSD, Pfizer, Roche Pharmaceuticals and Takeda. Joachim Ficker has received speaker honoraria from AstraZeneca, Bayer, Boehringer Ingelheim, Chugai, GSK, MSD, Novartis, Pfizer, Roche, and Sanofi-Aventis. Frank Griesinger has served on advisory councils or committees for Boehringer Ingelheim, Roche, and AstraZeneca; and has received honoraria, consulting fees, and grants or funds, from Boehringer Ingelheim, Roche, and Astra Zeneca. Stefan Krüger has received honoraria, and grants or funds, from Boehringer Ingelheim. Justyna Rawluk has served on advisory councils or committees for AstraZeneca, BMS, MSD, Boehringer Ingelheim, Roche, and Takeda; and has received consulting fees from AstraZeneca, BMS, MSD, Boehringer Ingelheim, Roche, and Takeda. Martin Reck has served on advisory councils or committees for AbbVie, Amgen, AstraZeneca, BMS, Boehringer Ingelheim, Celgene, Lilly, Merck, MSD, Novartis, Pfizer, Roche, and Sanofi; received speaker honoraria from AbbVie, AstraZeneca, BMS, Boehringer Ingelheim, Lilly, Merck, MSD, Novartis, Pfizer, and Roche; and received consulting fees from AbbVie, Amgen, AstraZeneca, BMS, Boehringer Ingelheim, Celgene, Lilly, Merck, MSD, Novartis, Pfizer, Roche, and Sanofi. Christopher Hoffman and Andrea Schüler are employees of Boehringer Ingelheim. Stephan Budweiser, Tobias Gaska, Cornelius Kortsik, Konrad Kokowski, Eckart Laack, and Harold Schäfer have no potential conflicts of interest to declare., (© The Author(s), 2021.)

Standard first-line treatment of aggressive B cell lymphoma comprises six or eight cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) plus eight doses of rituximab (R). Whether adding two doses of rituximab to six cycles of R-CHOP is of therapeutic benefit has not been systematically investigated. The Positron Emission Tomography-Guided Therapy of Aggressive Non-Hodgkin Lymphomas (PETAL) trial investigated the ability of [ 18 F]-fluorodesoxyglucose PET scanning to guide treatment in aggressive non-Hodgkin lymphomas. Patients with B cell lymphomas and a negative interim scan received six cycles of R-CHOP with or without two extra doses of rituximab. For reasons related to trial design, only about a third underwent randomization between the two options. Combining randomized and non-randomized patients enabled subgroup analyses for diffuse large B cell lymphoma (DLBCL; n = 544), primary mediastinal B cell lymphoma (PMBCL; n = 37), and follicular lymphoma (FL) grade 3 (n = 35). With a median follow-up of 52 months, increasing the number of rituximab administrations failed to improve outcome. A non-significant trend for improved event-free survival was seen in DLBCL high-risk patients, as defined by the International Prognostic Index, while inferior survival was observed in female patients below the age of 60 years. Long-term outcome in PMBCL was excellent. Differences between FL grade 3a and FL grade 3b were not apparent. The results were confirmed in a Cox proportional hazard regression model and a propensity score matching analysis. In conclusion, adding two doses of rituximab to six cycles of R-CHOP did not improve outcome in patients with aggressive B cell lymphomas and a fast metabolic treatment response.

Dose-dense induction with the S-HAM regimen was compared to standard double induction therapy in adult patients with newly diagnosed acute myeloid leukemia. Patients were centrally randomized (1:1) between S-HAM (2nd chemotherapy cycle starting on day 8 = "dose-dense") and double induction with TAD-HAM or HAM(-HAM) (2nd cycle starting on day 21 = "standard"). 387 evaluable patients were randomly assigned to S-HAM (N = 203) and to standard double induction (N = 184). The primary endpoint overall response rate (ORR) consisting of complete remission (CR) and incomplete remission (CR i ) was not significantly different (P = 0.202) between S-HAM (77%) and double induction (72%). The median overall survival was 35 months after S-HAM and 25 months after double induction (P = 0.323). Duration of critical leukopenia was significantly reduced after S-HAM (median 29 days) versus double induction (median 44 days)-P < 0.001. This translated into a significantly shortened duration of hospitalization after S-HAM (median 37 days) as compared to standard induction (median 49 days)-P < 0.001. In conclusion, dose-dense induction therapy with the S-HAM regimen shows favorable trends but no significant differences in ORR and OS compared to standard double induction. S-HAM significantly shortens critical leukopenia and the duration of hospitalization by 2 weeks.

Purpose Interim positron emission tomography (PET) using the tracer, [ 18 F]fluorodeoxyglucose, may predict outcomes in patients with aggressive non-Hodgkin lymphomas. We assessed whether PET can guide therapy in patients who are treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP). Patients and Methods Newly diagnosed patients received two cycles of CHOP-plus rituximab (R-CHOP) in CD20-positive lymphomas-followed by a PET scan that was evaluated using the ΔSUV max method. PET-positive patients were randomly assigned to receive six additional cycles of R-CHOP or six blocks of an intensive Burkitt's lymphoma protocol. PET-negative patients with CD20-positive lymphomas were randomly assigned or allocated to receive four additional cycles of R-CHOP or the same treatment with two additional doses rituximab. The primary end point was event-free survival time as assessed by log-rank test. Results Interim PET was positive in 108 (12.5%) and negative in 754 (87.5%) of 862 patients treated, with statistically significant differences in event-free survival and overall survival. Among PET-positive patients, 52 were randomly assigned to R-CHOP and 56 to the Burkitt protocol, with 2-year event-free survival rates of 42.0% (95% CI, 28.2% to 55.2%) and 31.6% (95% CI, 19.3% to 44.6%), respectively (hazard ratio, 1.501 [95% CI, 0.896 to 2.514]; P = .1229). The Burkitt protocol produced significantly more toxicity. Of 754 PET-negative patients, 255 underwent random assignment (129 to R-CHOP and 126 to R-CHOP with additional rituximab). Event-free survival rates were 76.4% (95% CI, 68.0% to 82.8%) and 73.5% (95% CI, 64.8% to 80.4%), respectively (hazard ratio, 1.048 [95% CI, 0.684 to 1.606]; P = .8305). Outcome prediction by PET was independent of the International Prognostic Index. Results in diffuse large B-cell lymphoma were similar to those in the total group. Conclusion Interim PET predicted survival in patients with aggressive lymphomas treated with R-CHOP. PET-based treatment intensification did not improve outcome.

To investigate GVL effects, Balb/c mice (H-2d) received 5 x 10(5) A20 (B cell leukemia) or 1 x 10(6) WEHI-3 (myelomonocytic leukemia) cells. These cell lines lead to death after a median of 19 (WEHI-3) or 30 days (A20). A lethal dose of total body irradiation followed by syngeneic BMT resulted in significantly prolonged survival of leukemia-bearing animals. Transplantation of (C57 x Balb/c)F1 (H-2bxd) allogeneic, but GVH-non-reactive marrow grafts differentially influenced the relapse rates in the two leukemia models. Whereas allogeneic BMT reduced the relapse rates in A20-bearing mice, the leukemia-free survival was not improved in mice bearing the leukemia WEHI-3 compared with syngeneic BMT. Pre-treatment of allogeneic (C57 x Balb/c)F1 or syngeneic Balb/c marrow cells with 200 U/ml IL-2 for 24 h did not reduce relapse rates in animals inoculated with A20 leukemia cells compared with unmanipulated bone marrow. In contrast, IL-2 treatment of syngeneic or allogeneic GVH non-reactive donor marrow significantly decreased the relapse rate in mice inoculated with WEHI-3 leukemia cells. The NK cell-mediated lysis of cultured leukemia cells was determined in vitro using a conventional 56Cr-release assay. Our data revealed a strong correlation between the level of natural killer activity determined in vitro and GVL activity in vivo.

We used a murine model to determine the impact of donor lymphocyte subsets on the incidence of primary marrow graft failure after transplantation of lymphocyte-depleted bone marrow. After lethal irradiation with 7.5 Gy, Balb/c mice received 1 x 10(5) to 4 x 10(7) GvH-nonreactive (C57 x Balb)F1 or GvH-reactive C57Bl/6 marrow cells. Pretreatment with anti-Thy-1.2, anti-CD4/CD8, anti-asialo-GM1 or L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) was employed to eliminate T lymphocytes and/or natural killer cells. Primary graft failure was defined as death with neutrophils < 0.5 x 10(9)/l. To assess long-term chimaerism, the percentage of H-2b-positive spleen cells was determined. Pretreatment with anti-Thy-1.2, anti-CD4/CD8 or Leu-Leu-OMe successfully eliminated GvHR-induced mortality. Graft failure rates gradually declined from 88% after transplantation of 1 x 10(5) cells to 0% after transplantation of 4 x 10(7) C57Bl/6 cells. The incidence of graft failure, however, was not altered by T-cell depletion, provided that the unspecific loss of marrow cells was compensated for. After transplantation of GvH-nonreactive (C57 x Balb)F1 bone marrow, neither ex-vivo treatment with anti-Thy-1.2 and anti-asialo GM1 nor addition of 1 x 10(7) donor thymocytes to the allograft significantly influenced engraftment. The data obtained in our animal model suggest that the total number of marrow cells is of critical importance for successful marrow engraftment and not the presence or absence of T cells, NK cells or GvHR.

The transfer of cytotoxic effector cells reduces the risk of relapse after allogeneic BMT. Two murine leukemia cell lines, A20 (B lymphocytic) and WEHI-3 (myelomonocytic), were used to investigate antileukemic effector mechanisms operating independently from graft-versus-host disease (GVHD). Different results were obtained with the two leukemia models. After injection of A20 cells, the majority of Balb/c recipients treated with syngeneic BMT died due to leukemia relapse (89%). The transplantation of MHC-matched DBA marrow resulted in chronic GvHD but did not reduce the risk of relapse (86%). Grafting of MHC-mismatched (but GvH-nonreactive) marrow cells from (C57xBalb)F1 hybrids, however, led to a significantly lower relapse rate (47%, p < 0.05). In vitro testing revealed that F1 cells but not Balb/c or DBA cells exert NK cell activity against A20. The elimination of NK 1.1-positive cells from the graft reduced the antileukemic activity of (C57xBalb)F1 marrow against A20 in vivo. After injection of WEHI-3 leukemia cells, syngeneic BMT cured most of the recipients (62%) and transplantation of (C57xBalb)F1 marrow provided no additional benefit. In contrast to unmanipulated Balb/c and (C57xBalb)F1 cells, which showed no NK activity against WEHI-3 in vitro, IL-2 treated effector cells were highly cytotoxic. Transfer of IL-2 preincubated grafts significantly decreased the relapse rate of WEHI-3 (19 vs. 38%) after syngeneic and allogeneic BMT. Our data indicate that GvL activity can be separated from GvHD. In our murine model, GvL activity appears to depend more on the donors NK/LAK cell activity than on the presence or absence of GvHD.

Graft rejection has hampered the use of T cell depletion (TCD) in allogeneic bone marrow transplantation. A model of host-versus-graft (HVGR) and graft-versus-host reaction (GVHR) as two inversely related processes has been proposed. We investigated graft rejection rates in graft-versus-host-reactive and graft-versus-host-nonreactive situations in a rat and a mouse model. Model 1: LEW rats were pretreated with a fixed myeloablative dose of busulfan and increasing doses of the immunosuppressive cyclophosphamide. The animals received different doses of semiallogeneic GvH-nonreactive BM cells. Graft rejection rates were dependent on the bone marrow cell number transplanted and on the pretransplant immunosuppression. Graft rejection rates following transplantation of GvH-reactive CAP marrow and genetically GvH-nonreactive (CAP x LEW)F1 marrow were the same. In conclusion, there was no advantage with respect to engraftment for the GvH-reactive marrow. Model 2: In irradiated Balb/c mice, graft rejection rates following T cell-depleted and unmanipulated transplantation of GvH-reactive or GvH-nonreactive bone marrow grafts were identical. All experiments were done with graded numbers of BM cells and revealed a strong impact of the BM cell dose on engraftment. In our experiments the cell loss during the ex-vivo manipulation was approximately 50% and, in contrast to the clinical situation, we readjusted to the intended number after TCD. Our experiments demonstrate that neither GvHR nor T cells but the BM cell dose has a strong impact on engraftment of allogeneic bone marrow.