A pilot trial of doxorubicin containing phosphatidyldiglycerol based thermosensitive liposomes in spontaneous feline soft tissue sarcoma.

PURPOSE: Doxorubicin (DOX)-loaded phosphatidyldiglycerol-based thermosensitive liposomes (DPPG2-TSL-DOX) combined with local hyperthermia (HT) was evaluated in cats with locally advanced spontaneous fibrosarcomas (soft tissue sarcoma [STS]). The study was designed to evaluate the safety and pharmacokinetic profile of the drug. Results from four dose-levels are reported. METHODS: Eleven client-owned cats with advanced STS were enrolled. Five cats received escalating doses of 0.1-0.4 mg/kg DOX (group I), three received 0.4 mg/kg constantly (group II) and three 0.6 mg/kg (group III) IV over 15 min. HT with a target temperature of 41.5 °C was started 15 min before drug application and continued for a total of 60 min. Six HT treatments were applied every other week using a radiofrequency applicator. Tumour growth was monitored by magnetic resonance imaging (MRI) and for dose level III also with 18F-FDG PET. RESULTS: Treatment was generally well tolerated and reasons for premature study termination in four cats were not associated with drug-induced toxicity. No DPPG2-TSL-DOX based hypersensitivity reaction was observed. One cat showed simultaneous partial response (PR) in MRI and positron emission tomography (PET) whereas one cat showed stable disease in MRI and PR in PET (both cats in dose level III). Pharmacokinetic measurements demonstrated DOX release triggered by HT. CONCLUSION: DPPG2-TSL-DOX + HT is a promising treatment option for advanced feline STS by means of targeted drug delivery. As MTD was not reached further investigation is warranted to determine if higher doses would result in even better tumour responses.

Use of Ronidazole and Limited Culling To Eliminate Tritrichomonas muris from Laboratory Mice.

Tritrichomonas muris is occasionally identified during routine fecal screening of laboratory mice. Frequently, entire racks are affected, and because no effective treatment is available, culling of affected mice and rederivation by embryo transfer have been suggested. The current study evaluated whether treatment with ronidazole, a nitroimidazole efficacious against T. fetus infections in cats, combined with limited culling was effective against T. muris in laboratory mice (Mus musculus). A subset (n = 39) of mice were treated with ronidazole (400 mg/L in drinking water) for 15 d, after which 6 of the mice still shed T. muris. Consequently all mice in the affected rack received ronidazole (500 mg /L in drinking water) for 25 d. All mice were retested by using pooled samples, and those positive for T. muris (except for a valuable breeding pair) were culled. The remaining mice continued to receive ronidazole for another 17 d. At the end of the treatment period, all mice were tested (days 60 and 81) and were shown to be negative for T. muris. Over the following year, sentinel mice from the rack were tested every 3 mo and remained negative for tritrichomonads by fecal smear. Thus, a combination of limited culling and treatment with ronidazole in the drinking water successfully cleared research mice of infection with T. muris.

Transplantation of CD6-depleted peripheral blood stem cells after DLA-haploidentical bone marrow transplantation contributes to engraftment and tolerance in a preclinical model of stem cell transplantation.

Human leukocyte antigen (HLA)-haploidentical stem cell transplantation is an opportunity for nearly all patients lacking an HLA matched stem cell donor. However, graft rejection and graft-versus-host disease (GvHD) as well as infectious complications still result in high treatment-related mortality. Here, we used the dog as a preclinical model for the study of tolerance induction with the aim to optimize and to improve a clinical protocol of haploidentical stem cell transplantation. For this purpose CD6-depleted peripheral blood stem cells (PBSCs) were transfused 6d after transplantation of unmodified bone marrow from dog leukocyte antigen (DLA)-haploidentical littermate donors in order to induce immune tolerance. Besides hematopoietic stem cells CD6-depleted PBSC contain, NK cells and a minority of suppressive CD8-positive cells that may suppress activated T lymphocytes. Recipients were conditioned with, cyclophosphamide and antithymocyte globulin (ATG) preceded by a transfusion of donor buffy coat and either 1, 2 or 3 × 3.3 Gy total body irradiation (TBI). Postgrafting immunosuppression was limited to 30 d of cyclosporine and methotrexate. The additional administration of CD6-depleted PBSCs after unmodified marrow could not prevent GvHD, but it may improve engraftment and chimerism after conditioning with 2 × 3.3 Gy TBI. Reasons for incomplete suppression and possible improvements for clinical applications are discussed.

Tolerance in DLA-haploidentical canine littermates following CD6-depleted marrow transplantation and donor lymphocyte transfusion.

OBJECTIVE: Donor lymphocyte transfusions (DLT) are effective in the treatment of leukemia after allogeneic stem cell transplantation. Graft-vs-host-disease (GVHD) is the major risk factor of DLT. In dog leukocyte antigen (DLA)-identical littermate dogs, DLT given within 3 weeks after transplantation of marrow depleted of T cells using absorbed antithymocyte globulin produced fatal GVHD, whereas at 2 months or later after transplantation, DLT were tolerated without GVHD. Here, we studied tolerance to DLT in DLA-haploidentical recipients of CD6-depleted bone marrow. MATERIALS AND METHODS: Bone marrow recipients were DLA-heterozygous and DLA-haploidentical to their DLA-homozygous donors. Marrow transplantation was performed on day 0, one day after total body irradiation with 10Gy. CD6 depletion was achieved by treatment of the marrow with CD6 antibody and rabbit complement. Natural killer cell activity of CD6-depleted cells was studied against canine thyroid adenocarcinoma cells. DLT were given at various time points after transplantation. RESULTS: Seven DLA-heterozygous dogs given undepleted marrow died of GVHD within 28 days. In contrast, three dogs given CD6-depleted marrow had sustained engraftment without occurrence of GVHD. DLT given on either day 3, 7, or 14 produced fatal GVHD. DLT on day 20, however, produced fatal GVHD in only two of four dogs. Mixed chimerism was converted into complete chimerism in all cases. Contrary to T-cell depletion with antithymocyte globulin, CD6 depletion spares canine natural killer cells. CONCLUSIONS: We conclude that T-cell depletion with CD6 antibody and complement induces graft-vs-host tolerance without jeopardizing engraftment. DLT on days 3, 7, and 14 after transplantation produced GVHD, but it failed to abrogate tolerance in two of four dogs transfused on day 20.