Coordination structure of the ferric heme iron in engineered distal histidine myoglobin mutants.

Recombinant human myoglobin mutants with the distal His residue (E7, His64) replaced by Leu, Val, or Gln residues were prepared by site-directed mutagenesis and expression in Escherichia coli. Electronic and coordination structures of the ferric heme iron in the recombinant myoglobin proteins were examined by optical absorption, EPR, 1H NMR, magnetic circular dichroism, and x-ray spectroscopy. Mutations, His-->Val and His-->Leu, remove the heme-bound water molecule resulting in a five-coordinate heme iron at neutral pH, while the heme-bound water molecule appears to be retained in the engineered myoglobin with His-->Gln substitution as in the wild-type protein. The distal Val and distal Leu ferric myoglobin mutants at neutral pH exhibited EPR spectra with g perpendicular values smaller than 6, which could be interpreted as an admixture of intermediate (S = 3/2) and high (S = 5/2) spin states. At alkaline pH, the distal Gln mutant is in the same so-called "hydroxy low spin" form as the wild-type protein, while the distal Leu and distal Val mutants are in high spin states. The ligand binding properties of these recombinant myoglobin proteins were studied by measurements of azide equilibrium and cyanide binding. The distal Leu and distal Val mutants exhibited diminished azide affinity and extremely slow cyanide binding, while the distal Gln mutant showed azide affinity and cyanide association rate constants similar to those of the wild-type protein.

EPR characterization of the stereochemistry of the distal heme pocket of the engineered human myoglobin mutants.

Recombinant human myoglobin mutants with the distal histidine residue replaced by Leu, Val, or Gln residues have been prepared by site-directed mutagenesis and expression in Escherichia coli. The recombinant apomyoglobin proteins have been successfully reconstituted with cobaltous protoporphyrin IX to obtain cobalt myoglobin mutant proteins, and the role of the distal histidine residue on the interaction between the bound ligand and the myoglobin molecule has been studied by EPR spectroscopy. We found that the distal histidine residue is significant in the orientation of the bound oxygen molecule. Low temperature photolysis experiments on both oxy cobalt proteins and ferric nitric oxide complexes indicated that the nature of the photolyzed form depends on the steric crowding of the distal heme pocket. To our surprise, the distal Leu mutant has a less restricted, less sterically crowded distal heme pocket than that of the distal Val mutant myoglobin, despite the fact that Leu has a larger side chain volume than Val. Our results demonstrate that the distal heme pocket steric crowding is not necessarily related to the side chain volume of the E7 residue.

Phase I study of tricyclic nucleoside phosphate using a five-day continuous infusion schedule.

A Phase I trial of tricyclic nucleoside phosphate (1,4,5,6,8-pentaazaacenaphthylene-3-amino-1, 5-dihydro-5-methyl-1-beta-D-ribofuranosyl 5'-phosphate ester; NSC 280594) was conducted using a 5-day continuous infusion schedule. Thirty-seven patients with advanced cancer were entered on the study, of whom 33 patients were evaluable for response and toxicity. Dose levels ranged from 10 mg/sq m/day X 5 days to 40 mg/sq m/day X 5 days. Initially, courses were repeated every 3 to 4 weeks. As cumulative toxicity became manifested, the interval between courses was changed to every 6 weeks. Major toxicities included hyperglycemia, hepatotoxicity, and thrombocytopenia. Patients with a prior history of diabetes mellitus, extensive radiation therapy, or significant liver metastases were prone to severe toxicity. Other toxicities noted were nausea and vomiting, abdominal discomfort, anemia, and reduction in serum calcium, phosphorus, and albumin levels. Rare side effects included hypertriglyceridemia, hyperamylasemia, diarrhea, and stomatitis. Antitumor activity observed include improvement in s.c. metastases in a patient with papillary thyroid carcinoma, stabilization of disease in a patient with mesothelioma, and mixed responses in three patients (colon cancer, sarcoma, and tonsillar squamous cell cancer). Recommended schedule for Phase II studies is 20 mg/sq m/day for 5 days every 6 weeks.

High-dose methotrexate with leucovorin rescue plus vincristine in advanced sarcoma: a Southwest Oncology Group study.

Twenty-six evaluable patients with advanced soft tissue and bony sarcomas refractory to chemotherapy were treated with vincristine plus high-dose methotrexate and leucovorin rescue. A 14% response rate was observed among 14 patients presenting with refractory soft tissue sarcomas. No responses were observed among 12 patients with bony sarcoma. Toxic reaction with nausea, vomiting, nephrotoxicity, and myelosuppression was manageable. While this study did demonstrate activity of this regimen in doxorubicin-refractory patients, the duration of the responses was relatively brief. Thus, the clinical utility of such a regimen is questionable.

Clinical pharmacology of the anticancer polypeptide neocarzinostatin.

The clinical pharmacology of the anticancer polypeptide neocarzinostatin was studied in 16 patients with disseminated neoplasia using a radioimmunoassay technique. Patients who received 2,400-3,600 U of the drug per square meter BSA by rapid IV infusion had triphasic plasma decay curves. For eight patients with normal hepatic and renal function, neocarzinostatin mean plasma half-lives were 0.14, 0.50, and 7.7 h. The mean plasma drug clearance was 32.4 ml/min/m2 and the apparent volume of distribution 19.3 l/m2. Two patients with liver dysfunction had shorter terminal plasma half-lives and greater drug clearance, while two with renal disease exhibited prolonged plasma half-lives and reduced drug clearances. The mean cumulative urinary excretion of neocarzinostatin was 69.1% of the administered dose at 72 h in three patients with normal hepatic and renal function. One patient with liver disease excreted 90.4%, while a patient with renal disease excreted only 58.1% of the dose in 24 h. In one patient with marked liver disease, biliary excretion accounted for 0.1% of the administered dose in 72 h. Cerebrospinal fluid concentrations of neocarzinostatin studied in two patients showed a CSF penetration of about 16% the plasma concentration at 1-5 h; concentrations persisted for 19 h in one patient with an Omayha reservoir. Neocarzinostatin was rapidly cleared from the plasma and eliminated in the urine. Dosage reductions of 50% are recommended for patients with impaired renal function, while no reduction or escalated doses could be tolerated by patients with liver disease. The pharmacologic data suggest a continuous IV infusion may be a more toxic but perhaps more effective schedule of administration.

Neocarzinostatin: report of a phase II clinical trial.

Fifty-three patients received intensive treatment with neocarzinostatin in doses of 3500 units/m2 by iv bolus infusion daily for 5-14 days. The response rate for 22 patients with leukemia was 9%. One complete and one partial remission were observed among nine patients with chronic myelogenous leukemia in blast cell crisis. None of the 31 patients with solid tumors responded to treatment. With this dose schedule, prolonged thrombocytopenia and cumulative bone marrow toxicity limit the intensity and duration of neocarzinostatin therapy. Acute allergic reactions occurred in 28% of the treatment courses, and three patients developed anaphylaxis during the second or third course of therapy.

The chemotherapy of lymphoblastic lymphoma.

Thirty-two patients treated on consecutive Southwest Oncology Group (SWOG) protocols for malignant lymphoma were subsequently diagnosed as having lymphoblastic lymphoma. Combination chemistry, usually adriamycin-based, produced complete responses (CR) in 17 patients (53%). Median survival was 15 mo. Patients achieving a CR survival significantly longer than patients with partial or no response (p < 0.01). Ten of 24 patients not receiving central nervous system (CNS) prophylaxis developed leptomeningeal lymphoma while none of the seven patients who received prophylactic intrathecal cytosine arabinoside or methotrexate developed CNS lymphoma (p = 0.04). Implications of these results for planning future treatment programs of lymphoblastic lymphoma are discussed.

Neocarzinostatin: a phase I clinical trial with five-day intermittent and continuous infusions.

Neocarzinostatin, a polypeptide antibiotic, was administered by both continuous and intermittent intravenous infusion to 76 patients with a variety of malignant diseases. Doses ranged from 500 to 6500 units/m2 X 5 days. With levels greater than or equal to 1800 units/m2, bone marrow suppression (particularly thrombocytopenia) was the dose-limiting toxicity. Delayed bone marrow recovery was less dose-dependent and occurred in 58% of initial treatment courses in solid tumor patients. Allergic reactions were more frequent with intermittent than with continuous infusions (20% vs. 2% of courses). No complete or partial remissions were observed among solid tumor patients although clinical improvement was noted in one patient with mycosis fungoides and one patient with multiple myeloma. One complete and two partial remissions were noted among 21 patients with acute leukemia. There was one complete remission in a patient with chronic leukemia. Leukemic patients on intermittent therapy evidenced greater change in bone marrow cellularity than those treated by continuous infusion. Although neocarzinostatin has some activity in the treatment of acute leukemia, continuous infusion offers no advantage over intermittent therapy.

Dichloroallyl lawsone.

Dichloroallyl lawsone (DCL, NSC-126771), a synthetic analogue of the antimalarial lapachol, is potentially useful in cancer chemotherapy. Unlike most anticancer agents, DCL is not significantly myelosuppressive in animals but it induces acute cardiac toxicity in the rhesus monkey. This cardiac toxicity seems to be correlated with the maximal plasma DCL concentration, about 130 mg/L in the monkey. We have studied DCL pharmacokinetics in patients in an attempt to define safe dose limits for the Phase I clinical trial. After the rapid intravenous infusion of 10 mg/m2 of radioactive [1- or 4-14C]DCL, 250 muCi per patient, the mean peak plasma concentration of unchanged DCL in four patients was 2.9 +/- 0.3 mg/L. The drug had a mean initial plasma half-life of 48.9 +/- 19 min and a terminal half-life of 20.3 +/- 1.8 hr, with a C X t of 50.1 +/- 12 mg/L/hr, and a clearance rate of 0.08 ml/kg/min. These data suggest that in clinical trials the DCL dose given by rapid intravenous infusion should not exceed 450 mg/m2 so that the maximal plasma drug concentration remains below 130 mg/L.

Combination chemotherapy for mycosis fungoides: a Southwest Oncology Group study.

Between 1972 and 1977, the Southwest Oncology Group studied the following three chemotherapy programs for the treatment of patients with advanced forms of mycosis fungoides: (a) cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP) (seven patients); (b) adriamycin, vincristine, and prednisone (HOP) (five patients); and (c) cyclophosphamide, vincristine, prednisone, and bleomycin (COP plus bleomycin) (12 patients). Among the 24 evaluable patients there was an overall objective response rate of 95% with seven (29%) achieving a complete remission. With the adriamycin-containing chemotherapy, five (42%) of 12 patients achieved a complete remission compared to two (17%) of 12 patients treated with COP plus bleomycin. The median duration of remission (partial plus complete) was longer with the COP plus bleomycin combination (median, 47 weeks) than with the adriamycin-containing combinations (median, 22 weeks; P = 0.03). The median survival for all 24 evaluable patients was 95 weeks and was similar regardless of remission-induction therapy. In summary, combination chemotherapy proved to be effective palliative therapy for advanced mycosis fungoides.

Cyclocytidine chemotherapy for malignant melanoma.

Twenty-nine patients with metastatic malignant melanoma were treated with cyclocytidine, 240 mg/m2/day sc for 10 days. All partients had received extensive prior chemotherapy. Only one patient achieved a partial remission; the overall response rate (complete plus partial) was 4%. Unusual toxic effects associated with cyclocytidine chemotherapy included the delayed onset of thrombocytopenia, orthostatic hypotension, and jaw pain.

Curability of non-Hodgkin's lymphomas.

The relapse rates of patients with malignant lymphoma have been analyzed in relation to the number of patients in complete remission (CR) at yearly intervals after the onset of therapy. Several different patterns of relapse have been identified. Patients in CR from nodular poorly differentiated lymphocytic lymphoma have a low rate of recurrent disease (14%) during the first year of treatment but rates of relapse in succeeding years have not decreased. Patients with diffuse poorly differentiated lymphocytic lymphoma have a significantly higher relapse rate during the first year of treatment (33%). However, remission duration curves suggest that the risk of relapse is decreasing with time. Patients with diffuse histiocytic lymphoma, who initially have the greatest risk of disease recurrence (42%), subsequently showed a significant fall in their rate of relapse. As many as 50% of these patients who attain a CR may have been cured of their disease. An analysis of CR duration curves may be used to determine the effective doubling time of various malignant diseases and to estimate cure rates within a few years after the onset of therapy.

Chemotherapy of non-Hodgkin's lymphoma: 10 years' experience in the Southwest Oncology Group.

The Southwest Oncology Group (SWOG) has completed five studies of high-dose intermittent combination chemotherapy for the management of advanced (stage III and IV) non-Hodgkin's lymphoma involving 1143 patients from May 1966 to September 1974. Lack of uniform histopathologic interpretation precludes precise analysis of these data. Although there has been little change in complete response duration over the years of this study, there has been an overall improvement in response rate and survival though there is no statistically significant improvement in the best overall survival when compared to the Stanford experience in stage III and IV disease (1960-71). The response rate and survival in diffuse histiocytic lymphoma have improved since the first study. There is definite evidence of a plateau in the survival curve beyond 2 years. The percentage of survival at which the plateau appears has increased over the years to 40% in the most recent studies, and the survival is suggestively better than the Stanford experience (P = 0.09). Over the years there has been a distinct improvement in response rate and survival of patients with nodular lymphocytic lymphoma, although the best SWOG survival is no different than the Stanford experience (P = 0.36).

Combination chemotherapy ("CHOP-Bleo") in advanced (non-Hodgkin) malignant lymphoma.

Forty-seven adults with advanced malignant lymphoma (the majority in stage IV) were treated with a combination of cyclophosphamide, hydroxyldaunorubicin (Adriamycin), vincristine (Oncovin), prednisone, and bleomycin (CHOP-Bleo). The complete remission (CR) rate was 66%. The overall response (complete + partial remission) was 92%. The CR rate in patients with diffuse histiocytic lymphoma (DHL) was 69%. Only 3 of the 18 patients with DHL in CR have relapsed; the projected median duration of response was calculated to be greater than 2 yr. In patients with nodular poorly differentiated lymphocytic lymphoma (NPDL), the CR rate was 62%. One of the eight patients with NPDL in CR has relapsed; the projected median duration of complete response will be greater than 4 yr. The median survival for all patients entered in this study has not been reached; however, it was estimated that it will be greater than 3 yr. The survival curves became flat at 70 wk for the patients with DHL and at 1 yr for the patients with NPDL. Major complications during chemotherapy with CHOP-Bleo were myelosuppression and alopecia. Only six severe infections occurred during myelosuppression. No hemorrhagic problems were observed. This study indicates that combination chemotherapy with these agents is effective in increasing the CR rate and survival in patients with diffuse histiocytic lymphoma. In patients with NPDL, further observation will be needed to assess the effect of this combination on survival.

Combination chemotherapy with bis chloroethyl nitrosourea (BCNU), vincristine and dimethyl triazeno imidazole carboxamide (DTIC) in disseminated malignant melanoma.

One hundred thirty two patients with disseminated malignant melanoma were treated using a combination of BCNU, vincristine and imidazole carboxamide. A response rate of 23% was observed, while 16% had stable disease. The patients' median survival was 42 months from diagnosis and 5.3 months from the onset of treatment. These results are not significantly different from therapy with imidazole carboxamide alone. Patients on this study were observed to have a significant reduction in the number of lymphocytes in their peripheral blood (mean 1800/mm3, median 1550/mm3). Patients with lymphopenia prior to the onset of therapy (86%) had a similar response rate but a shorter median survival (4.4 months vs. 7.8 months, P = .03) than patients with normal lymphocyte levels. These findings are compatible with recent observations on the importance of host immunocompetence in patients with malignant melanoma. Eosinophil levels were not closely correlated with response, although among patients with eosinophil counts of greater than 300/mm3 (22%), a slightly higher response rate (29%) was observed (P = .13). Eosinophilia did not influence patient survival.