Therapy of Myeloid Leukemia using Novel Bispecific Fusion Proteins Targeting CD45 and 90Y-DOTA

Pretargeted radioimmunotherapy (PRIT) has been investigated as a multi-step approach to decrease relapse and toxicity for high-risk acute myeloid leukemia (AML). Relevant factors including endogenous biotin and immunogenicity, however, have limited the use of PRIT with an anti-CD45 antibody streptavidin conjugate and radiolabeled DOTA-biotin. To overcome these limitations we designed anti-murine and anti-human CD45 bispecific antibody constructs using 30F11 and BC8 antibodies, respectively, combined with an anti-yttrium (Y)-DOTA single-chain variable fragment (C825) to capture a radiolabeled ligand. The bispecific construct targeting human CD45 (BC8-Fc-C825) had high uptake in leukemia HEL xenografts [7.8 ± 0.02% percent injected dose/gram of tissue (% ID/g)]. Therapy studies showed that 70% of mice with HEL human xenografts treated with BC8-Fc-C825 followed by 44.4 MBq (1,200 μCi) of ⁹⁰Y-DOTA-biotin survived at least 170 days after therapy, while all nontreated controls required euthanasia because of tumor progression by day 32. High uptake at sites of leukemia (spleen and bone marrow) was also seen with 30F11-IgG1-C825 in a syngeneic disseminated SJL murine leukemia model (spleen, 9.0 ± 1.5% ID/g and bone marrow, 8.1 ± 1.2% ID/g), with minimal uptake in all other normal organs (<0.5% ID/g) at 24 hours after ⁹⁰Y-DOTA injections. SJL leukemia mice treated with the bispecific 30F11-IgG1-C825 and 29.6 MBq (800 μCi) of ⁹⁰Y-DOTA-biotin had a survival advantage compared with untreated leukemic mice (median, 43 vs. 30 days, respectively; P < 0.0001). These data suggest bispecific antibody-mediated PRIT may be highly effective for leukemia therapy and translation to human studies.

Allogeneic transplantation for advanced acute myeloid leukemia: The value of complete remission

BACKGROUND

Patients with acute myeloid leukemia (AML) without complete remission (CR) or in first relapse (Rel1) can have extended leukemia control and survival after allogeneic hematopoietic cell transplantation (HCT). For patients in Rel1 or primary induction failure (PIF), transplantation versus treatment to achieve a second CR (CR2) and subsequent HCT might yield similar outcomes, but available comparative data are scarce.

METHODS

Survival was analyzed in 4682 HCT recipients according to disease status: PIF (N = 1440), Rel1 (failing ≥1 reinduction; N = 1256), and CR2 (N = 1986).

RESULTS

Patient, disease, and transplantation characteristics were similar, except that patients in CR2 more often had performance scores of 90% to 100%, de novo AML, and longer CR1 duration. Adverse cytogenetics were more common in patients who experienced PIF. The 5-year survival rate adjusted for performance score, cytogenetic risk, and donor type for CR2 was 39% (95% confidence interval [CI], 37%-41%) compared with 18% (95% CI, 16%-20%) for HCT in Rel1 and 21% (95% CI, 19%-23%) in PIF (P < .0001).

CONCLUSIONS

Although survival is superior for patients who undergo HCT in CR2, transplantation for selected patients in Rel1 or PIF may still be valuable. These data can guide decision making about additional salvage therapy versus prompt HCT for patients not in CR, but they also highlight that AML is intrinsically more treatable in patients who have favorable-risk cytogenetics, those with longer CR1 duration, and younger patients with better performance status. Cancer 2017;123:2025-2034. © 2017 American Cancer Society.

Reduced intensity conditioned allograft yields favorable survival for older adults with B-cell acute lymphoblastic leukemia

Older adults with B-cell acute lymphoblastic leukemia (B-ALL) have poor survival. We examined the effectiveness of reduced intensity conditioning (RIC) hematopoietic cell transplant (HCT) in adults with B-ALL age 55 years and older and explored prognostic factors associated with long-term outcomes. Using CIBMTR registry data, we evaluated 273 patients (median age 61, range 55-72) with B-ALL with disease status in CR1 (71%), >CR2 (17%) and Primary Induction Failure (PIF)/Relapse (11%), who underwent RIC HCT between 2001 and 2012 using mostly unrelated donor (59%) or HLA-matched sibling (32%). Among patients with available cytogenetic data, the Philadelphia chromosome (Ph+) was present in 50%. The 3-year cumulative incidences of nonrelapse mortality (NRM) and relapse were 25% (95% confidence intervals (CI): 20-31%) and 47% (95% CI: 41-53%), respectively. Three-year overall survival (OS) was 38% (95% CI: 33-44%). Relapse remained the leading cause of death accounting for 49% of all deaths. In univariate analysis, 3 year risk of NRM was significantly higher with reduced Karnofsky performance status (KPS <90: 34% (95% CI: 25-43%) versus KPS ≥90 (18%; 95% CI: 12-24%, P = 0.006). Mortality was increased in older adults (66+ vs. 55-60: Relative Risk [RR] 1.51 95% CI: 1.00-2.29, P = 0.05) and those with advanced disease (RR 2.13; 95% CI: 1.36-3.34, P = 0.001). Survival of patients in CR1 yields 45% (95% CI: 38-52%) at 3 years and no relapse occurred after 2 years. We report promising OS and acceptable NRM using RIC HCT in older patients with B-ALL. Disease status in CR1 and good performance status are associated with improved outcomes. Am. J. Hematol. 92:42-49, 2017. © 2016 Wiley Periodicals, Inc.

Urinary elafin and kidney injury in hematopoietic cell transplant recipients

BACKGROUND AND OBJECTIVES

Graft-versus-host disease (GVHD) is associated with kidney injury after hematopoietic cell transplantation (HCT). Because plasma elafin levels correlate with skin GVHD, this study examined urinary elafin as a potential marker of renal inflammation and injury.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urine was collected prospectively on 205 patients undergoing their first HCT from 2003 to 2010. Collections were done at baseline, weekly through day 100, and monthly through year 1 to measure elafin and urine albumin-to-creatinine ratio (ACR). Associations between urinary elafin levels and microalbuminuria, macroalbuminuria, AKI and CKD, and mortality were examined using Cox proportional hazards or linear regression models. Available kidney biopsy specimens were processed for immunohistochemistry.

RESULTS

Mean urinary elafin levels to day 100 were higher in patients with micro- or macroalbuminuria (adjusted mean difference, 529 pg/ml; P=0.03) at day 100 than in those with a normal ACR (adjusted mean difference, 1295 pg/ml; P<0.001). Mean urinary elafin levels were higher in patients with AKI compared with patients without AKI (adjusted mean difference, 558 pg/ml; P<0.01). The average urinary elafin levels within the first 100 days after HCT were higher in patients who developed CKD at 1 year than in patients without CKD (adjusted mean difference, 894 pg/ml; P=0.002). Among allogeneic recipients, a higher proportion of patients with micro- or macroalbuminuria at day 100 also had grade II-IV acute GVHD (80% and 86%, respectively) compared with patients with a normal ACR (58%; global P<0.01). Each increase in elafin of 500 pg/ml resulted in a 10% increase in risk of persistent macroalbuminuria (hazard ratio, 1.10; 95% confidence interval [95% CI], 1.06 to 1.13; P<0.001) and a 7% increase in the risk of overall mortality (95% CI, 1.02 to 1.13, P<0.01). Renal biopsy specimens from a separate cohort of HCT survivors demonstrated elafin staining in distal and collecting duct tubules.

CONCLUSION

Higher urinary elafin levels are associated with an increased risk of micro- and macroalbuminuria, AKI and CKD, and death after HCT.

Vaccination as a treatment for breast or ovarian cancer

The immune system recognizes breast and ovarian cancer cells but whether it is effective in controlling these cancers in patients has yet to be proven. The challenge with vaccination strategies is to break tolerance so that the patient's immune system will recognize cancer cells. The success of vaccines depends on the identification of appropriate tumor antigens, establishment of effective immunization strategies and their ability to circumvent inhibitory immune mechanisms.

Urinary cytokines after HCT: evidence for renal inflammation in the pathogenesis of proteinuria and kidney disease

We compared urinary levels of cytokines in patients with and without albuminuria, proteinuria, and kidney disease (GFR < 60 ml/min/1.73m²) after hematopoietic cell transplant (HCT). Plasma and urine were collected at baseline and weekly through day-100 and monthly through year-1, for measurement of IL-6, gp130, sIL6r, IL10, IL15, MCP1 and urine albumin to creatinine ratios (ACR). Cox-proportional hazards modeling examined associations between urinary cytokine levels and development of these renal endpoints. The association of ACR with the hazard of overall mortality was assessed using Cox regression.

Increasing urinary IL-6 and IL-15 were associated with an increased risk of developing proteinuria. Urinary MCP-1 during the first 100 days post-HCT was associated with kidney disease at 1 year. The degree of albuminuria at any time point in the first 100 days post-transplant was related to the subsequent risk of death (for ACR 30-299, HR=1.91; 95%CI:1.27-2.87; for ACR >300, HR=2.82; 95%CI:1.60-4.98).

After HCT, elevated urinary levels of proinflammatory cytokines are associated with development of albuminuria and proteinuria, suggesting early intrarenal inflammation as an important pathogenetic mechanism. Albuminuria and proteinuria within the first 100 days post-HCT are associated with decreased overall survival.

Timing and severity of community acquired respiratory virus infections after myeloablative versus non-myeloablative hematopoietic stem cell transplantation

BACKGROUND

Respiratory virus infections are important causes of morbidity and mortality after hematopoietic cell transplantation. Their clinical course can be severe with progression to lower respiratory tract infection, co-infection with serious pulmonary co-pathogens, and high mortality. Non-myeloablative conditioning regimens achieve engraftment without eradication of host hematopoietic cells, which potentially allows for protection against infections commonly seen in hematopoietic cell transplantation patients treated with standard intensity conditioning regimens.

DESIGN AND METHODS

We performed a retrospective cohort study to measure the incidence and severity of parainfluenza types 1-4, influenza (A and B), respiratory syncitial virus and human rhinovirus disease in myeloablative versus non-myeloablative versus autologous hematopoietic cell transplantation patients.

RESULTS

The incidences of all respiratory virus infections were similar in the non-myeloablative and myeloablative cohorts but less in the autologous cohort (33/420 [7.9%], 150/1593 [9.4%], and 37/751 [4.9%], respectively, p<0.0001). However, respiratory virus lower tract infections were significantly less common during the first 100 days after transplantation in non-myeloablative patients compared to myeloablative and autologous patients (1/420 [0.2%], 34/1593 [2.1%] and 16/751 [2.1%], respectively, p=0.005. Respiratory virus lower tract infection had high co-infection and attributable mortality rates.

CONCLUSIONS

Respiratory virus lower tract infection during the first 100 days after hematopoietic cell transplantation was less common in persons receiving non-myeloablative conditioning regimens compared to myeloablative conditioning, despite a similar overall rate of acquisition.

Reduced-intensity conditioning regimen workshop: defining the dose spectrum. Report of a workshop convened by the center for international blood and marrow transplant research

During the 2006 BMT Tandem Meetings, a workshop was convened by the Center for International Blood and Marrow Transplant Research (CIBMTR) to discuss conditioning regimen intensity and define boundaries of reduced-intensity conditioning (RIC) before hematopoietic cell transplantation (HCT). The goal of the workshop was to determine the acceptance of available RIC definitions in the transplant community. Participants were surveyed regarding their opinions on specific statements on conditioning regimen intensity. Questions covered the "Champlin criteria," as well as operational definitions used in registry studies, exemplified in clinical vignettes. A total of 56 participants, including transplantation physicians, transplant center directors, and transplantation nurses, with a median of 12 years of experience in HCT, answered the survey. Of these, 67% agreed that a RIC regimen should cause reversible myelosuppression when administered without stem cell support, result in low nonhematologic toxicity, and, after transplantation, result in mixed donor-recipient chimerism at the time of first assessment in most patients. Likewise, the majority (71%) agreed or strongly agreed that regimens including < 500 cGy of total body irradiation as a single fraction or 800 cGy in fractionated doses, busulfan dose < 9 mg/kg, melphalan dose <140 mg/m(2), or thiotepa dose < 10 mg/kg should be considered RIC regimens. However, only 32% agreed or strongly agreed that the combination of carmustine, etoposide, cytarabine, and melphalan (BEAM) should be considered a RIC regimen. These results demonstrate that although HCT professionals have not reached a consensus on what constitutes a RIC regimen, most accept currently used criteria and operational definitions. These results support the continued use of current criteria for RIC regimens until a consensus statement can be developed.

Impact of acute kidney injury on long-term mortality after nonmyeloablative hematopoietic cell transplantation

Acute kidney injury (AKI) occurs frequently after nonmyeloablative hematopoietic cell transplantation (HCT). The severity of AKI after nonmyeloablative HCT has association with short-term mortality. However, the long-term effect of AKI on survival after nonmyeloablative HCT is not known. We performed a retrospective analysis of patients who underwent an HLA matched nonmyeloablative HCT between 1997 and 2006. Patients were followed for a median of 36 (range: 3-99) months. AKI occurring up to day 100 was defined as a >2-fold increase in serum creatinine or requirement of dialysis. Of the 358 patients who were included in the analysis, 200 (56%) had AKI, 158 (44%) had no AKI. Overall, 158 patients (43%) died during follow-up. After controlling for potential confounders, the adjusted hazard ratio for overall mortality associated with AKI was 1.57 (95 % confidence interval [CI] 1.2-2.3; P = .0006). The adjusted hazards ratio of nonrelapse mortality (NRM) associated with AKI was 1.72 (95% CI 0.9-3.1; P = .07). AKI is an independent predictor of overall mortality after nonmyeloablative HCT. This finding reiterates the importance of identifying preventative strategies in nonmyeloablative HCT for attenuating incidence and severity of AKI.

Results of donor lymphocyte infusions for relapsed myelodysplastic syndrome after hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) represents a potentially curative approach for patients with myelodysplastic syndromes (MDSs). While a large proportion of HCT recipients become long-term disease-free survivors, recurrence of MDS remains the leading cause of mortality after HCT. The role of donor lymphocyte infusion (DLI) in patients with relapsed MDS after HCT is unclear. We report results among 16 patients treated with DLI for relapsed MDS after HCT at a single institution between March 1993 and February 2004. The cohort contained 10 men and 6 women with a median age of 49 (range, 22-67) years. CR with resolution of cytopenias and prior disease markers occurred in 3 of 14 patients who could be evaluated. Two patients survived without MDS for 68 and 65 months after DLI, respectively, but died with pneumonia. Grades II-IV acute GVHD and chronic GVHD occurred after DLI in 6 (43%) and 5 (36%) patients, respectively. All three responders developed grades III-IV acute GVHD and extensive chronic GVHD after DLI. Our results confirm prior reports that DLI can result in CR in some patients with recurrent MDS after transplant, but long-term survival is infrequent.

Nonmyeloablative hematopoietic cell transplantation (HCT) for treatment of patients (pts) with fludarabine-refractory chronic lymphocytic leukemia (CLL) results in prolonged median survival

6520

Background: Pts with fludarabine-refractory CLL have a poor prognosis with median survival of 12 months. A phase II trial of Campath resulted in median survival of 16 months. Curative alternatives are required. Methods: We previously reported 2-year overall survival (OS) of 60% for 64 pts treated with nonmyeloablative HCT from related (n=44) or unrelated (n=20) donors (Sorror. JCO, 2005). Those pts were refractory to fludarabine (88%) ± additional agents. Eligibility criteria, conditioning and immunosuppression regimens, and primary endpoint were previously described. Here, we extended the follow up to 38 (range: 10–74) months after HCT ( Table ). Results: Chronic extensive graft-versus-host disease (GVHD) at 3 years was 53% and non-relapse mortality (NRM) was 27%. Among 30 pts who achieved initial responses {25 complete (CR) and 5 partial (PR)}, one patient died while in CR from NRM, one patient with PR progressed, while remaining 28 pts continued alive and in remission. CR and relapse rate at 3 years were 54% and 32%, respectively. Unrelated recipients had a significantly higher CR rate than related recipients. Ten responding pts were tested for molecular eradication of their disease and all were negative at a median of 52 months. There were 6 deaths in this extended follow up, 5 from relapse/progression and one from pneumonia. Overall, 33 pts are alive; 24 in CR, 4 in PR, 2 with stable disease, and 3 with relapse/progression. Estimated 3-year rates of OS, disease-free survival (DFS), and NRM were 54%, 42%, and 27% respectively. In multivariate analysis, high pretransplant comorbidity scores predicted higher NRM and worse OS while bulky lymphadenopathy predicted increased risk of progression. Conclusion: Nonmyeloablative HCT resulted in an extended median survival of greater than 3 years for pts with fludarabine-refractory CLL. The use of unrelated grafts was associated with a trend toward better DFS.

[Table: see text]

No significant financial relationships to disclose.

Immunologic recovery after hematopoietic cell transplantation with nonmyeloablative conditioning

OBJECTIVE

We studied immune reconstitution in 51 recipients of HLA-identical hematopoietic cellular transplant (HCT) after nonmyeloablative conditioning compared to a reference group of 67 recipients after myeloablative conditioning.

METHODS

Nonmyeloablative conditioning consisted of 2 Gy total-body irradiation+/-fludarabine and postgrafting cyclosporine and mycophenolate mofetil. All patients received G-CSF-mobilized peripheral blood mononuclear cells. Patients were followed with serial assessments of lymphocyte subset counts, antibody levels, virus-induced lymphoproliferation, and limiting-dilution assays for cytomegalovirus (CMV) T helper (T(H)) cells. Rates of infections over the first year after transplant were calculated.

RESULTS

During the first 180 days, absolute lymphocyte subset counts were similar (except higher total and memory B cell counts on day 80 in nonmyeloablative patients). At 1 year, however, total and naïve CD4 counts, and naïve CD8 counts, were higher in myeloablative patients. The levels of antibodies were similar at all time points and after vaccinations. The function of CD4 cells assessed by virus-induced lymphoproliferation was similar. However, the absolute counts of CMV T(H) cells were higher at days 30 and 90 (p=0.002 and p=0.0003, respectively) after nonmyeloablative conditioning. The rates of definite infections were lower for nonmyeloablative patients during the first 90 days, but were higher later. The higher number of CMV-specific T cells days 30 and 90 after nonmyeloablative HCT coincided with a lower rate of CMV infections during that time.

CONCLUSION

The immunity of nonmyeloablative HCT recipients appears better than the immunity of conventional HCT recipients early, but not late, after HCT.

Reduced toxicity and prompt engraftment after minimal conditioning of a patient with Fanconi anemia undergoing hematopoietic stem cell transplantation from an HLA-matched unrelated donor

Given the profound sensitivity of patients with Fanconi anemia to conventional conditioning regimens before hematopoietic stem cell transplantation (HSCT), we developed a minimally toxic regimen consisting of 2 Gy total body irradiation, 90 mg/m2 fludarabine, and postgrafting immunosuppression with cyclosporine and mycophenolate to treat FA patients undergoing HSCT from HLA-matched unrelated donors. With over 10 months follow-up, our first patient has complete and sustained engraftment. Graft-versus-host disease was limited to mild skin and liver and moderate gut manifestations. We conclude that the approach is well tolerated and ideally suited to reduce regimen-related toxicities while achieving sustained engraftment.

Nonmyeloablative hematopoietic cell transplantation. Replacing high-dose cytotoxic therapy by the graft-versus-tumor effect

Conventional allografting produces considerable regimen-related toxicities that generally limit this treatment to patients younger than 55 years and in otherwise good medical condition. T cell-mediated graft-versus-tumor (GVT) effects are known to play an important role in the elimination of malignant disease after allotransplants. A minimally myelosuppressive regimen that relies on immunosuppression for allogeneic engraftment was developed to reduce toxicities while optimizing GVT effects. Pre-transplant total-body irradiation (200 cGy) followed by post-transplant immunosuppression with cyclosporine (CSP) and mycophenolate mofetil (MMF) permitted human leukocyte antigen (HLA)-matched sibling donor hematopoietic cell engraftment in 82% of patients (n = 55) without prior high-dose therapy. The addition of fludarabine (90 mg/m2) facilitated engraftment in all 28 subsequent patients. Overall, fatal progression of underlying disease occurred in 20% of patients after transplant. Non-relapse mortality occurred in 11% of patients. Toxicities were low. Grade 2-4 acute graft-versus-host disease (GVHD) associated with primary engraftment developed in 47% of patients, and was readily controlled in all but two patients. Donor lymphocyte infusions (DLI) were not very effective at converting a low degree of mixed donor/host chimerism to full donor chimerism; however, the addition of fludarabine reduced the need for DLI. With a median follow-up of 244 days, 68% of patients were alive, with 42% of patients in complete remission, including molecular remissions. Remissions occurred gradually over periods of weeks to a year. If long-term efficacy is demonstrated, such a strategy would expand treatment options for patients who would otherwise be excluded from conventional allografting.

Canine CD34: cloning of the cDNA and evaluation of an antiserum to recombinant protein

Increasingly, enriched populations of hematopoietic progenitors are used in experimental and clinical transplantation studies. The separation of progenitors is based on the expression of CD34, a marker preferentially expressed on progenitor cells. The dog model has been important for preclinical transplant studies, because it has proven predictive for outcomes in human hematopoietic stem cell transplantation. To identify and isolate canine hematopoietic progenitors, we have cloned a cDNA encoding a CD34 homologue from a canine myelomonocytic leukemia cell line, ML2. The CD34 homologue cDNA predicts an amino acid sequence that is highly conserved with human and murine CD34 in the cytoplasmic domain, transmembrane domain, and C-terminal end of the extracellular domain, but shows considerable divergence from these sequences at the amino-terminal end of the protein. In Western blotting studies, canine CD34 homologue (caCD34) appears to be a heavily and variably glycosylated protein with a molecular weight of approximately 100 kD and shows some tissue-specific differences in protein mass. To evaluate the expression of caCD34 protein, the extracellular domain of caCD34 was expressed as an Ig fusion protein and used as an immunogen to generate a rabbit polyclonal antiserum. The antiserum reacted against the fusion protein, against vascular endothelium, and with three leukemic cell lines. Approximately 1% of canine bone marrow cells stained brightly with antibodies to caCD34 and this population was 25- to 50-fold enriched for colony-forming units-granulocyte-macrophage as compared to unfractionated marrow mononuclear cells. These findings suggest that the canine CD34 homologue is expressed on bone marrow progenitor cells and, thus, that this molecule should be a valuable marker for identifying and isolating canine hematopoietic progenitors for experimental hematopoiesis and stem cell transplantation.

High-dose fractionated total-body irradiation, etoposide, and cyclophosphamide followed by autologous stem-cell support in patients with malignant lymphoma

PURPOSE

To evaluate a high-dose treatment regimen of fractionated total-body irradiation (TBI), etoposide, and cyclophosphamide (Cy) followed by autologous stem-cell transplantation (ASCT) in patients with malignant lymphoma.

PATIENTS AND METHODS

Fifty-three patients with non-Hodgkin's lymphoma (NHL; n = 43) or Hodgkin's disease (HD; n = 10) received 12.0 Gy of fractionated TBI, etoposide 60 mg/kg, and Cy 100 mg/kg followed by infusion of autologous hematopoietic stem cells.

RESULTS

Thirty-one of 53 patients are alive a median of 643 (range, 177 to 1,144) days after transplant. The 2 year Kaplan-Meier (K-M) estimates of survival, event-free survival (EFS), and relapse for all 53 patients were 54%, 45%, and 43%, respectively. Sixteen of 24 patients with less advanced disease and 10 of 29 patients with more advanced disease survive free of disease for K-M estimates of EFS of 61% and 31%, respectively (P = .006). The K-M estimates of relapse were 34% for patients with less advanced disease and 53% (P = .05) for patients with more advanced disease. The K-M estimates of dying from causes other than relapse were 8% in patients with less versus 25% in patients with more advanced disease (P = .09).

CONCLUSION

These data indicate that approximately 60% of patients transplanted early after failure of initial therapy for malignant lymphoma are projected to be disease-free more than 2 years after treatment with fractionated TBI, etoposide, and Cy and infusion of autologous hematopoietic stem cells. The transplant-related mortality rate is low and relapse is the main cause of treatment failure in patients with less advanced disease. For patients with more advanced disease, the K-M estimates of both transplant-related deaths (25%) and relapse (53%) remain major problems.

Phase I study of high-dose busulfan, melphalan and thiotepa with autologous stem cell support in patients with refractory malignancies

The purpose of this study was to determine the maximal tolerated dose of thiotepa administered with busulfan 12 mg/kg and melphalan 100 mg/m2 followed by autologous stem cell transplantation in patients with refractory malignancies. Twenty-eight patients with refractory malignancies received high-dose busulfan 12 mg/kg, melphalan 100 mg/m2 and escalating doses of thiotepa 450-550 mg/m2 followed by infusion of cryopreserved autologous peripheral blood stem cells (n = 26) or marrow (n = 2). The maximum tolerated dose was determined to be busulfan 12 mg/kg, melphalan 100 mg/m2 and thiotepa 500 mg/m2. Two of three patients receiving thiotepa 550 mg/m2 experienced grade 3 colitis. Twenty patients were enrolled at the maximum tolerated dose and the incidence of grade 3-4 regimen-related toxicity and mortality was 10% and 5%, respectively. Ninety-five per cent of patients experienced grade 1-2 mucositis, 50% grade 1-2 gastrointestinal toxicity, 35% grade I hepatic toxicity and 20% experienced grade 1-2 skin toxicity. The median time to achieve a granulocyte count of 0.5 x 10(9)/I was 10 days (range 8-20 days) and platelet transfusion independence was 10 days (range 1-26 days). Five of ten patients with stage 4 refractory breast cancer achieved a complete and two a partial remission with a complete response rate of 50% and a overall response rate of 70%. In conclusion, busulfan, melphalan and thiotepa can be administered in high doses with tolerable mucositis as the major side-effect. This combination has significant activity in patients with breast cancer, and phase II studies in patients with breast cancer and other chemotherapy sensitive malignancies are warranted.

Effects of propylthiouracil on the biodistribution of an iodine-131-labeled anti-myeloid antibody in normal dogs: dosimetry and clinical implications

Despite the use of near maximal doses of chemoradiotherapy, tumor recurrence remains the most frequent cause of treatment failure following marrow transplantation for leukemia. We have previously demonstrated that it is possible to selectively deliver radiation to the marrow space. In that study an initial short half-life of the radionuclide was observed. In this study we attempted to prolong the retention of the radioiodine in marrow through the use of propylthiouracil (PTU). When administered to normal dogs, PTU pretreatment resulted in improved marrow localization of 131I-labeled DM-5. There was no appreciable loss of activity from the marrow during the 2-4 hr postinjection time interval; a finding in contrast to the control animals where marrow activity declined a mean 45 +/- 0.5% over the same time period. Additionally, in contrast to controls, a rise in plasma trichloroacetic acid (TCA) nonprecipitable activity was not demonstrated in the PTU treated group during this 2-4 hr period. These results suggest that PTU's inhibition of deiodinases resulted in longer residence time of the radionuclide in its target tissue without adversely affecting distribution to non-target organs.

Failure of anti-MHC antibodies to prevent GVHD in DLA mismatched unrelated canine marrow recipients

Gene products of the major histocompatibility complex (MHC) have been shown to elicit lethal graft-versus-host disease (GVHD) in experimental animals. Antibodies specific for MHC cell surface determinants might therefore be expected to overcome histocompatibility barriers and influence survival of marrow graft recipients. GVHD can be consistently induced in dogs by transplanting donor marrow cells into lethally irradiated, unrelated, mismatched recipients. Three anti-Ia monoclonal antibodies were administered to five canine recipients, each at a dose of 0.2 mg/kg body weight per day intravenously for 10 days, beginning on day 0, the day of transplantation. Eight canine recipients were treated with antidog alloantiserum 10 ml/kg body weight per day intravenously on days -2 to day +20, in addition to receiving postgrafting methotrexate. The antiserum was generated by immunizing a matched littermate of the donor with peripheral blood cells of the recipient before transplantation. Survival was no different in the two groups of dogs, compared with historical controls without antibody treatment. A possible explanation for the failure of anti-MHC antibodies to modify acute GVHD in the dog is the inability of antibody to reach critical tissue sites targeted in GVHD.

Specific marrow localization of an 131I-labeled anti-myeloid antibody in normal dogs: effects of a "cold" antibody pretreatment dose on marrow localization

Tumor recurrence and regimen-related toxicity remain major obstacles in the successful use of marrow transplantation as therapy for hematologic malignancies. By attaching radionuclides to monoclonal antibodies (MoAbs) targeted at myeloid-associated antigenic determinants, a more effective and directed delivery of therapy may be possible without increasing toxicity. We investigated the biodistribution over time of an anti-myeloid antibody (DM-5) labeled with trace amounts of 131I in normal dogs. This study demonstrates the ability to target marrow with a high degree of selectivity, achieving marrow/blood ratios of 25-30:1 with the greatest concentration in any other organ being a tissue/blood ratio of 1.4:1 for stomach at 48 h. A pretreatment dose of unlabeled antibody effectively reduced early hepatic uptake by 80%, resulting in improved marrow localization with an estimated 58.6% of the injected dose localized in marrow within 2 h following infusion, compared to 32.8% without pretreatment. The marrow concentration clearance curve for the radioimmunoconjugate revealed an initial short half-life (4.75 h), suggesting rapid internalization, digestion, and release of free iodine (dehalogenation). This view was supported by a corresponding rise in trichloroacetic acid-non-precipitable activity during this period. Methods aimed at decreasing dehalogenation may result in longer residence time of the radionuclide within the marrow space, resulting in more effective tumor cell kill. This approach may provide a way to improve upon the current results obtained with marrow transplantation as treatment for patients with leukemia and other hematologic malignancies.

Use of trimetrexate for the prevention of graft-versus-host disease

The effects of trimetrexate following marrow transplantation were studied in a dog model. Four animals were given 9.2 Gy total body irradiation (TBI), autologous marrow, and either trimetrexate alone (0.4 mg/kg on days 1, 3, 6, and 11) or combined with cyclosporine (CSP) (15 mg/kg per day i.m. on days 1-7, then orally until day 25, then taper). All four animals engrafted normally, demonstrating that trimetrexate at this dose is tolerable. Ten additional animals were given a similar dose of TBI followed by marrow and buffy coat cells from littermate donors differing for one DLA haplotype. Trimetrexate and CSP were given as noted above. Four of the 10 animals died, one with septicemia prior to engraftment (day 14), one with intussusception (day 28), one with graft failure (day 32) and one with a tracheal abscess without graft-versus-host disease (GVHD) (day 67). Six dogs survived in excess of 100 days; one of the six developed chronic GVHD. These results are superior to those previously achieved with either methotrexate or CSP as single agents and are roughly equivalent to results achieved with a combination of methotrexate and CSP in similarly mismatched donor-recipient pairs.

Antibody-radionuclide conjugates as part of a myeloablative preparative regimen for marrow transplantation

The behaviors of an anti-Ia antibody (7.2) and an antibody directed at a lymphocyte adhesion molecule (S.5) radiolabeled with 131I were studied in normal dogs. Antibody 7.2 localized to spleen and, to a lesser extent, to marrow and lymph nodes. Antibody S.5 rapidly localized to marrow and spleen, achieving tissue/blood ratios greater than 6:1 within three hours of injection that were maintained for at least 48 hours. Prior treatment with cyclophosphamide (CY) markedly altered the distribution of S.5 but had much less effect on the distribution of 7.2 and almost no effect on the distribution of a control antibody. When animals were treated with increasing doses of 131I labeled to S.5, lethal myelosuppression occurred when a dose of 6 mCi/kg was reached. At this dose, the otherwise lethal effects of 131I could be reversed with autologous marrow transplant support.

L-leucyl-L-leucine methyl ester treatment of canine marrow and peripheral blood cells. Inhibition of proliferative responses with maintenance of the capacity for autologous marrow engraftment

Incubation of canine marrow and peripheral blood mononuclear cells with L-leucyl-L-leucine methyl ester resulted in the inhibition of mitogen- and alloantigen-induced blastogenesis, the elimination of allosensitized CTL and NK activity, and prevented the development of CTL from pCTL. The effects of these incubations were similar to those described in mice and humans. Additionally, in vitro CFU-GM growth from treated canine marrow was reduced, but could be regained when the Leu-Leu-OMe-treated marrow was cocultured with either untreated autologous peripheral blood mononuclear cells or monocyte-enriched PBMC but not with untreated monocyte-depleted PBMC. Six of seven dogs conditioned with 920 cGy total-body irradiation engrafted successfully after receiving autologous marrow that was incubated with Leu-Leu-OMe prior to infusion. These cumulative results indicate that incubation with Leu-Leu-OMe is a feasible method to deplete canine marrows of alloreactive and cytotoxic T cells prior to transplantation.