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Spirogermanium: effects on hematopoietic stem cells and survival of normal and tumor-bearing mice.

The effect of spirogermanium (SG) on hematopoietic stem cells, tumor burden, and survival times was investigated in C3H mice with transplanted mammary carcinoma. Compared to normal mice, the number of hematopoietic stem cells, or colony-forming units per spleen (CFU-S), was lower in the marrow of tumor-bearing mice. Spirogermanium at 15 and 30 mg/kg was not toxic to the normal hematopoietic cells in the marrow of either normal or tumor-bearing mice. In contrast to animals treated with cyclophosphamide, SG did not decrease the tumor growth rate or prolong the survival times of tumor-bearing C3H mice. Doses of 35-40 mg/kg SG did not prolong the survival times or decrease the tumor burden of AKR/J mice with a long-passaged lymphoma. These studies demonstrate that SG has minimal inhibitory effects to the marrow of normal mice and may promote the maintenance of normal marrow cells in tumor-bearing animals. However, in two different transplanted tumor cell lines, SG did not inhibit tumor growth or prolong host survival time.

Animals↗

In vitro and in vivo murine metabolism of spirogermanium.

We report the identification of spirogermanium (SG) metabolites derived from incubation of the drug with a mouse liver microsomal preparation as well as those obtained from the urine of mice injected with the drug. GC/MS data using electron impact and chemical ionization indicate that the major metabolic products appearing in the urine of mice are hydroxylated metabolites resulting from oxidation of the ethyl substituents on germanium. Thermospray (TSP) LC/MS data suggest that these hydroxy metabolites are further oxidized to an acid and a deethylated metabolite that has undergone hydroxylation of the germanium atom. In a separate experiment, human urine from a subject undergoing therapy with SG was subjected to TSP-LC/MS analysis. The SG metabolite pattern observed in the urine from human was similar to that observed in the mouse urine. These results suggest that the metabolic fate of SG in human is qualitatively similar to that found in the mouse.

Animals↗

Potential drugs for elimination of acute lymphatic leukemia cells from autologous bone marrow.

Five drugs, selected because of minimal in vivo myelotoxicity, have been investigated for inhibition of the growth of three acute lymphatic leukemia-derived cell lines. Granulocyte-macrophage colony-forming units (GM-CFU) inhibition with these five drugs after 60-min incubation was first established. Drug concentrations giving up to 90% kill of GM-CFU were then used. Spirogermanium and L-asparaginase did not have an effect on any of the three cell lines under the culture conditions tested, while 4-hydroperoxycyclophosphamide (4-HC) and vincristine inhibited the growth of all three cell lines tested, and bleomycin inhibited the growth of two cell lines. In addition to 4-HC, bleomycin and vincristine should be considered as possible agents in eliminating leukemic cells from autologous marrow grafts. These drugs also deserve further investigation in clonal systems.

Antineoplastic Agents↗

Evaluation of drugs for elimination of leukemic cells from the bone marrow of patients with acute leukemia.

Relatively nonmyelotoxic drugs and drug combinations were investigated for their ability to eliminate malignant cells from human bone marrow. In vitro 90% inhibitory concentration (IC90) doses were established on granulocyte macrophage colony-forming units (GM-CFU) in culture of bone marrow by using the GM-CFU assay for the following drugs: 4-hydroperoxycyclophosphamide (4-HC), Adriamycin, L-asparaginase, bleomycin, hydrocortisone, VP-16, spirogermanium, Taxol, and vincristine. The leukemic cell kill efficiency of these drugs at IC90 doses was compared with that of 4-HC on acute lymphoid leukemia (ALL) cell lines by using the limiting-dilution assay. Under these conditions, no single drug was superior to 4-HC. To increase the in vitro effect in leukemic cell kill, combinations of vincristine with hydrocortisone, Adriamycin, VP-16, and 4-HC were investigated. Vincristine at 1 to 5 micrograms/mL increased the marrow cytotoxicity of hydrocortisone, Adriamycin, and VP-16, but it was protective (subadditive) with 4-HC. Vincristine and 4-HC in combination was additive to supraadditive on ALL cell lines, increased the leukemic cell kill by one to two logs above 4-HC alone at IC90 doses (P less than .05), and was not affected by the addition of excess marrow cells. The recommended doses for chemopurging in clinical studies are vincristine, 1 to 5 micrograms/mL, plus 4-HC, 5 micrograms/mL.

Antineoplastic Agents↗

Phase I trial of spirogermanium given by infusion in a multiple-dose schedule.

In a phase I study of spirogermanium, a new azaspiran-germanium compound, 28 patients were given a multiple-dose schedule. When infused over 1 hour, the maximum tolerated single dose of this agent was greater than 120 mg/m2 but significant chronic neurologic toxicity occurred after 1-2 weeks of treatment. Patients with a poor performance status (PS) were the most likely to manifest toxic reactions. Suggested phage II dose levels for infusion treatment with spirogermanium are 120 mg/m2 for patients with a PS of 0-2 and 80 mg/m2 for patients with a PS of 3.

Adult↗

Phase I clinical trial of spirogermanium.

Spirogermanium is a new azaspirane antitumor agent, with the metal germanium substituted for a one-carbon moiety in the ring structure. This drug inhibits DNA and RNA synthesis in HeLa cells, is cytotoxic in vitro, and has curative in vivo antitumor activity against the ascitic Walker 256 carcinosarcoma in rats. No hematologic toxicity was recorded during the preclinical toxicologic evaluation. The principal clinical toxic effects observed in this phase I trial were neurologic, manifested as lethargy, dizziness, and ataxia, while a grand mal seizure was produced after an accidental overdose. There was no evidence of hematologic, renal, or hepatic toxicity. A partial response was achieved in a patient with a well-differentiated lymphocytic lymphoma. We recommend that phase II trials be conducted with a twice or thrice weekly dose of 50-80 mg/m2, administered in a 30-minute iv infusion.

Adult↗