SMANCS and polymer-conjugated macromolecular drugs: advantages in cancer chemotherapy

This review discusses the development and therapeutic potential of prototype macromolecular drugs for use in cancer chemotherapy, in particular the development and use of SMANCS, a conjugate of neocarzinostatin and poly(styrene-comaleic acid). The various topics covered include a brief description of the chemistry and polymer conjugation, the binding of the conjugate to albumin and the biological behaviour in vitro and in vivo after arterial injection in animals, including plasma half-life, and the lipid solubility of SMANCS in medium chain triglycerides and Lipiodol, a lipid contrast medium suitable for use in X-ray-computed tomography. The biological response-modifying effects and the tumor-targeting mechanism of SMANCS and other macromolecular drugs are also discussed. The latter mechanism is accounted for in terms of a tumor 'enhanced permeability and retention' (or EPR) effect. A principal advantage in the use of SMANCS or other macromolecular drugs is the potential for a reduction or elimination of toxicity. Macromolecular drugs such as a pyran copolymer-NCS conjugate show a marked reduction in bone marrow toxicity normally associated with the use of NCS. This is believed to be due to a hypothetical blood-bone marrow 'barrier' which, relative to NCS, restricts or limits access of the macromolecular drug to the bone marrow. In addition, the clinical possibilities for SMANCS are discussed, including the suggestion that angiotensin II-induced hypertension has clinical potential in improving the selective delivery of macromolecular drugs (i.e. SMANCS) to tumors. Aqueous SMANCS formulations have been tested in pilot studies in patients with solid tumors of the ovary, esophagus, lung, stomach, adrenal gland and in the brain. Formulations based on SMANCS/Lipiodol have been shown to be effective both as a diagnostic tool and for therapeutic use in solid tumors where the formulations are given arterially via a catheter. In a pilot study in primary unresectable hepatoma, an objective reduction in tumor size was observed for about 90% of cases when an adequate amount of the macromolecular drug was administered. A patient receiving such treatment with no active liver cirrhosis and tumor nodules/lesion confined within one liver segment might expect to have a 90% chance of survival after treatment for at least 5 years.

Effect of arterial administration of high-molecular-weight anticancer agent SMANCS with lipid lymphographic agent on hepatoma: a preliminary report

A clinical evaluation of arterial infusion of high-molecular-weight antitumor agent SMANCS dissolved in lipid lymphographic agent (thiodol) in 44 patients with mostly unresectable hepatoma is described. The treatment regimen demonstrated significant merits both therapeutically and diagnostically. Marked antitumor effects were shown in the decreased serum alpha-fetoprotein levels (86% of cases) and tumor size (95% of cases), and in survival period and histological findings. Furthermore, there was increased diagnostic sensitivity using CT scan, plain X-rays or ultrasound. The procedure of selective arterial administration of 3-4 mg of SMANCS in 3-4 ml of ethiodol per dose was simple to perform and was required only once every 3-4 weeks. Both ethiodol and the drug accumulated more selectively in tumor than in any other tissues and their activity remained for more than 3 weeks. Only minimal side-effects were associated with SMANCS and ethiodol during this study.

Cytotoxic drug-induced pulmonary disease: update 1980

Administration of a number of cytotoxic agents has been associated with interstitial pneumonitis, alveolitis and pulmonary fibrosis. Some (bleomycin, busulfan, methotrexate) are well known to cause this problem, and others (carmustine, semustine, zinostatin, mitomycin, and chlorambucil) have only recently been recognized to do so. We review and update the available information about this form of drug toxicity. Interaction between these drugs and thoracic radiation or high oxygen fractions in inspired air has produced pneumonitis at doses lower than when the drug is used alone. Synergism between the drugs themselves when given concurrently also produces pulmonary toxicity at lower doses. With some drugs and in some patients steroids will diminish the pulmonary abnormalities, but death from hypoxia is a frequent outcome. Since early recognition of the problem and withdrawal of the injurious agent is the best treatment, physician awareness of and alertness to this toxicity and its relative risk is most important. The discovery of analogs of bleomycin with a better therapeutic index, specifically reducing pulmonary damage, is one of the goals of current cancer drug development.

Transarterial chemotherapy alone versus transarterial chemoembolization for hepatocellular carcinoma: a randomized phase III trial

BACKGROUND/AIMS

Transcatheter arterial chemoembolization (TACE) is a combination of transarterial infusion chemotherapy (TAI) and embolization, and has been widely used to treat patients with hepatocellular carcinoma (HCC). However, since the impact of adding embolization on the survival of patients treated with TAI had never been evaluated in a phase III study, we conducted a multi-center, open-label trial comparing TACE and TAI to assess the effect of adding embolization on survival.

METHODS

Patients with newly diagnosed unresectable HCC were randomly assigned to either a TACE group or a TAI group. Zinostatin stimalamer was injected into the hepatic artery, together with gelatin sponge in the TACE group and without gelatin sponge in the TAI group. Treatment was repeated when follow-up computed tomography showed the appearance of new lesions in the liver or re-growth of previously treated tumors.

RESULTS

Seventy-nine patients were assigned to the TACE group, and 82 were assigned to the TAI group. The two groups were comparable with respect to their baseline characteristics. At the time of the analysis, 51 patients in the TACE group and 58 in the TAI group had died. The median overall survival time was 646 days in the TACE group and 679days in the TAI group (p=0.383).

CONCLUSIONS

The results of this study suggest that treatment intensification by adding embolization did not increase survival over TAI with zinostatin stimalamer alone in patients with HCC.

Processing of 3'-phosphoglycolate-terminated DNA double strand breaks by Artemis nuclease

The Artemis nuclease is required for V(D)J recombination and for repair of an as yet undefined subset of radiation-induced DNA double strand breaks. To assess the possibility that Artemis acts on oxidatively modified double strand break termini, its activity toward model DNA substrates, bearing either 3'-hydroxyl or 3'-phosphoglycolate moieties, was examined. A 3'-phosphoglycolate had little effect on Artemis-mediated trimming of long 3' overhangs (> or =9 nucleotides), which were efficiently trimmed to 4-5 nucleotides. However, 3'-phosphoglycolates on overhangs of 4-5 bases promoted Artemis-mediated removal of a single 3'-terminal nucleotide, while at least 2 nucleotides were trimmed from identical hydroxyl-terminated substrates. Artemis also efficiently removed a single nucleotide from a phosphoglycolate-terminated 3-base 3' overhang, while leaving an analogous hydroxyl-terminated overhang largely intact. Such removal was completely dependent on DNA-dependent protein kinase and ATP and was largely dependent on Ku, which markedly stimulated Artemis activity toward all 3' overhangs. Together, these data suggest that efficient Artemis-mediated cleavage of 3' overhangs requires a minimum of 2 nucleotides, or a nucleotide plus a phosphoglycolate, 3' to the cleavage site, as well as 2 unpaired nucleotides 5' to the cleavage site. Shorter 3'-phosphoglycolate-terminated overhangs and blunt ends were also processed by Artemis but much more slowly. Consistent with a role for Artemis in repair of terminally blocked double strand breaks in vivo, human cells lacking Artemis exhibited hypersensitivity to x-rays, bleomycin, and neocarzinostatin, which all induce 3'-phosphoglycolate-terminated double strand breaks.

Neocarzinostatin versus m-AMSA or doxorubicin in hepatocellular carcinoma

Sixty-one of 76 patients entered on a prospective randomized trial of neocarzinostatin ( NCZ ) versus m-AMSA or doxorubicin were eligible for analysis. Among these 61 patients at least one episode of severe toxicity was documented in 39% of patients on NCZ and 58% on m-AMSA. Fifty-one of the 61 patients were previously untreated with chemotherapy. Among these 51 patients objective response was documented in two of 25 patients treated with NCZ , none of 17 treated with m-AMSA, and one of nine treated with doxorubicin. Among previously untreated North American and European (NA/E) patients the median survival times were: NCZ 11 weeks and m-AMSA 12 weeks. The data on South African (SA) patients with similar entrance criteria entered on earlier Eastern Cooperative Oncology Group trials were analyzed with that from the randomized trial and show that for SA patients the median survival times were: NCZ , 11 weeks (31 patients); m-AMSA, 13 weeks (33 patients); and doxorubicin, 15 weeks (29 patients).

Tumor-targeted chemotherapy with SMANCS in lipiodol for renal cell carcinoma: longer survival with larger size tumors

OBJECTIVES

To evaluate the anticancer effects of a lipophilic macromolecular anticancer agent, poly(styrene-co-maleic acid)-conjugated neocarzinostatin (SMANCS), dissolved in a lipid contrast medium (Lipiodol) given via the renal artery to patients with renal cell carcinoma.

METHODS

Among 467 patients with renal cell carcinoma treated between April 1984 and March 1993, 191 were treated with SMANCS dissolved in a lipid contrast medium (a 3:2 mixture of Lipiodol F and Lipiodol Ultrafluid; Lpd). Selective arterial infusion of SMANCS/Lpd was performed at a dose of 1.0 or 1. 5 mg/mL. The infusion was repeated at intervals of about 2 weeks or longer, but the doses and the total number of infusions varied among patients, according to results of computed tomography analysis.

RESULTS

Statistical analysis was performed for 415 patients who met the criteria of this study. Twenty-six surgical patients with metastases who underwent infusion therapy of SMANCS/Lpd for primary lesions showed 3 and 5-year survival rates of 23.0% and 12.8%, respectively; the rates were 19.3% and 9.7% in 31 patients who did not receive SMANCS infusion therapy. In 125 surgical patients without metastases who underwent SMANCS/Lpd infusion, the 5 and 10-year survival rates were 83.0% and 75.2%, respectively, whereas rates of 84.6% and 78.9% were observed in 199 surgical patients whose median tumor size was significantly smaller, however, than the SMANCS/Lpd infusion group. The maximal tumor diameter at the beginning of treatment was significantly larger (mean diameter 70.8 mm) in the SMANCS/Lpd infusion group than in the noninfusion group (59.1 mm). The survival rate was statistically better for patients with tumors of 100 mm diameter or larger in the SMANCS/Lpd infusion group (P <0.05): 5 and 10-year survival rates were 70.4% and 61.6%, respectively, for the infusion group and 64.6% and 50.9% for the group receiving no drug. In patients with larger tumor (greater than 110 mm), the survival rate at 13 years was 75% in the SMANCS/Lpd infusion group and 0% in the surgery group.

CONCLUSIONS

Arterial infusion therapy with SMANCS/Lpd appears to be effective for large renal cell carcinoma without metastases in conjunction with surgery.

Transcatheter arterial embolization with zinostatin stimalamer for hepatocellular carcinoma

Zinostatin stimalamer (SMANCS) is a lipophilic intra-arterial chemotherapeutic agent for hepatocellular carcinoma (HCC). In our previous study, transcatheter arterial infusion chemotherapy using SMANCS for HCC showed a response rate of 20%. In an effort to obtain a superior anti-tumor effect against HCC, we conducted a phase II study of transcatheter arterial embolization (TAE) using SMANCS and gelatin sponge in 50 chemotherapy-naive patients with HCC. Four milligrams SMANCS plus 4 ml lipiodol emulsion was injected into the hepatic artery, followed by an injection of gelatin sponge. The responses were evaluated by computed tomography (CT) 1 month after treatment and thereafter every 3-4 months. One patient (2%) showed complete response and 15 patients (30%) had partial response resulting in an overall response rate of 32% (16/50; 95% confidence interval 19-45%). In 33 patients (66%), the disease remained stable, and 1 patient (2%) showed progressive disease. In 35 patients (70%), the rate of necrotic area to whole tumor was more than 50% according to the evaluation method using lipiodol accumulation in CT. The 1-, 3- and 5-year survival rates were 90, 55 and 19%, respectively. Grade 3 hematological toxicity was observed as thrombocytopenia in 2 patients (4%). Grade 3 and 4 non-hematological toxicity (liver dysfunction) occurred in 17 (34%) and 7 patients (14%), respectively. TAE using SMANCS, which was well tolerated, may be an effective treatment for advanced HCC.

A phase II study of neocarzinostatin (NSC 157365) in malignant hepatoma. An Eastern Cooperative Oncology Group pilot study

Thirty evaluable patients with histologically confirmed primary liver cancer (PLC) were treated with neocarzinostatin (NCS). All patients had measurable disease and an Eastern Cooperative Oncology Group (ECOG) performance status of 1, 2, or 3. NCS 2250 units/m2 was given daily for 5 days, repeated at 28-day intervals. Hemopoietic suppression was the major side effect. In 23 of 30 patients (13 with leukopenia and 19 with thrombocytopenia), this toxic effect was documented. Other toxic effects included nausea, vomiting, allergic-type reaction, and elevation of NPN. Partial response, with a median duration of 12.7 weeks (range 4--37 weeks) was observed in seven patients. In nine patients the response was classified as no change, and in 14 patients there was progressive disease. NCS has some therapeutic activity in patients with PLC.

Transarterial chemotherapy with zinostatin stimalamer for hepatocellular carcinoma

Zinostatin stimalamer (SMANCS) is a lipophilic intra-arterial chemotherapeutic agent for hepatocellular carcinoma (HCC). Thirty HCC patients underwent transcatheter arterial injection of 4 mg SMANCS-lipiodol emulsion. Their responses were evaluated by computed tomography 1 month after treatment. Complete response (CR) was defined as disappearance or 100% necrosis of all tumors. Partial response (PR) was defined as > or = 50% reduction and/or > or = 50% necrosis. We regarded the lipiodol accumulation in tumors as being necrotic. CR and PR were observed in 8 patients (27%) and 4 patients (13%), respectively, and the overall response rate (CR + PR/all patients) was 40% (12/30). Of 12 patients whose serum alpha-fetoprotein levels had been more than 200 ng/ml before treatment, 5 patients (42%) showed more than 50% reduction in this level within 1 month after treatment. Toxicity was quite acceptable, although grade 4 toxicity (WHO) was observed as liver dysfunction in 1 patient. Transarterial chemotherapy with SMANCS, which is well tolerated, appears to have moderate antitumor effect in patients with HCC.

Neocarzinostatin (NSC 157365) a new cancerostatic compound

Neocarzinostatin is a new anticancer drug developed by Japanese investigators. In order to delineate the potential usefulness of this drug, we have reviewed the preclinical data and summarized the Japanese clinical data on 462 patients. The bulk of these patients had carcinoma of the stomach or pancreas and acute leukemia. Neocarzinostatin was administered intravenously in a daily dose of 2-3 mg for five to 15 day periods. Significant antitumor activity was observed in acute leukemia. A few responses were also reported in pancreatic adenocarcinoma, but the drug was inactive against gastric carcinoma. The side effects observed included nausea, vomiting, myelosuppression, fever, and occasional hypersensitivity reactions. The Investigational Drug Branch of the National Cancer Institute has recently sponsored an investigational new drug application with the Food and Drug Administration, and phase I studies are expected to begin soon in the United States.

Trans-catheter hepatic arterial injection of lipiodol soluble anti-cancer agent SMANCS and ADR suspension in lipiodol combined with arterial embolization and local hyperthermia for treatment of hepatocellular carcinoma

The clinical effect and safety of Lp-TAE alone and combined with radiofrequency (RF) capacitive hyperthermia (HT) were evaluated in 20 patients with hepatocellular carcinoma (HCC) associated with cirrhosis of the liver. After the oily carcinostatic agents were administered by Lp-TAE, HT, at a temperature of greater than 42.5 degrees C, was induced for 40 min, twice a week by an RF of 8 MHz for a total of 10 to 38 times. The response rate was 40% in the 10 cases that were treated with Lp-TAE combined with HT and 20% in the 10 cases that were treated with Lp-TAE. The patients who were treated with Lp-TAE combined with HT had a tendency to have better survival rates than those of the Lp-TAE group (p less than 0.099). The main side-effects of Lp-TAE combined with HT were low-grade fever, localized pain, myelo-suppression and liver dysfunction, but these were transient and eventually disappeared.

Reduced bone marrow toxicity of neocarzinostatin by conjugation with divinyl ether-maleic acid copolymer

Neocarzinostatin (NCS) was conjugated with divinyl ether-maleic acid anhydride copolymer (pyran copolymer), and its therapeutic effect was compared with that of NCS. The conjugated NCS (pyran-NCS) with a molecular weight of about 23,000, exhibited in vitro cytotoxic activity against eight cell lines and bone marrow cells that was similar to the cytotoxic activity of NCS on a molar basis. Furthermore, both drugs had similar effects against a multidrug-resistant Chinese hamster ovary cell line (CHR C5) and its parent cell line (AUXB1) in vitro. However, pharmacological analysis showed that pyran-NCS had reduced accumulation in the spleen, and most important was three times less hematotoxic in vivo compared with NCS. Also, pyran-NCS had a 1.7-fold higher 50% lethal dose (LD50). Antitumor activity of pyran-NCS and NCS was tested against two different forms of Meth A tumor. In a solid tumor model, pyran-NCS and NCS suppressed tumor growth at three-fourths of the LD50 to 12.8 and 19.0% of the control tumor as evaluated on day 28, respectively (P less than 0.025). In an ascitic tumor model, the percentage increase in the median life span caused by pyran-NCS and NCS was more than 400 and 150% on day 60, respectively. Pyran-NCS is more effective than NCS because the reduced acute toxicity permits an increased drug dosage.

Nausea and vomiting induced by arterial chemo-embolization in patients with hepatocellular carcinoma and the antiemetic effect of ondansetron hydrochloride

To determine the incidence of nausea and vomiting and the antiemetic effect of ondansetron hydrochloride (OND) in patients with hepatocellular carcinoma treated with arterial chemo-embolization, we studied 59 patients with hepatocellular carcinoma who were treated with transcatheter arterial embolization (TAE) or lipiodolized transcatheter arterial infusion (L-TAI). We investigated the incidence of nausea and vomiting and the amount of food intake when TAE or L-TAI was performed. All patients who experienced nausea and vomiting received OND administered prophylactically at the time of the next TAE or L-TAI to evaluate the antiemetic effect of the drug. Cumulative rates of nausea and vomiting during the week following arterial chemo-embolization were 44.8% and 27.6%, respectively. There was a tendency for the incidence to be higher in patients treated with the anticancer agent zinostatin stimalamer (SMANCS) than in those treated with epirubicin hydrochloride (EPI). Regarding food intake, 53.1% of the patients stated that they ate "half or more than half" of the food provided on the day of arterial chemo-embolization. The rate improved as time went on. In 5 patients who experienced nausea and vomiting at the time of arterial chemo-embolization, nausea and vomiting were inhibited satisfactorily by OND. When arterial chemo-embolization was performed, antiemetic treatment for approximately 3 days was necessary to improve patients' quality of life (QOL) to an acceptable level, and OND was found to be effective for the purpose in our 5 patients who had experienced nausea and/or vomiting at the previous treatment.

A novel dosage approach for evaluation of SMANCS [poly-(styrene-co-maleyl-half-n-butylate) - neocarzinostatin] in the treatment of primary hepatocellular carcinoma

We report a Phase I/II clinical trial of poly-(styrene-co-maleyl-half-n-butylate)-neocarzinostatin (SMANCS) for intra-arterial treatment of hepatoma. Early patients received 4 or 8 mg SMANCS dissolved in Lipiodol; later patients were treated according to tumour size and degree of filling achieved. SMANCS/Lipiodol drained rapidly from normal liver but was retained within tumour interstitium. Tumour nodules filled with SMANCS/Lipiodol usually stabilised and often regressed. No UICC criteria-defined responses were achieved, partly due to difficulties of filling several lesions simultaneously. Signs of therapeutic activity suggest a more extensive clinical study is warranted.

Multiple hepatic infarction after transcatheter arterial infusion with SMANCS

We report a patient with hepatocellular carcinoma who developed multiple hepatic infarction after transcatheter arterial infusion (TAI) with a suspension of styrene maleic acid neocarzinostatin (SMANCS) and Lipiodol (SMANCS/Lipiodol). The parameters of hepatic functional reserve were apparently decreased after the second TAI with SMANCS/Lipiodol, and the patient died of hepatic failure 103 days after the second TAI. The autopsy liver specimen revealed multiple hepatic infarctions associated with peripheral arterial stenosis or occlusion, and portal thrombosis. It is speculated that both the arterial occlusion and the portal thrombosis caused the hepatic infarction, based on a long-term insufficiency of blood supply to the hepatocytes arising from toxic arteritis caused by SMANCS/Lipiodol.

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.

[Phase II study of YM881 (zinostatin stimalamer) suspension injected into the hepatic artery. Research Group for Intra-arterial Injection Therapy with YM881]

A phase II study of YM 881 (zinostatin stimalamer) to determine the response and safety was conducted in patients with hepatocellular carcinoma by injecting a suspension of the drug into the hepatic artery. Repeated doses of 4 to 6 mg of the drug were given every 4 weeks so that the tumor tissues were filled with the suspension. Of the 195 registered patients, 15 were ineligible for the study, 8 dropped out, and data were missing for 5. A total of 167 patients completed the study. Response was assessed in the 167 patients who completed the study. CR was found in one, PR in 59, MR in 25, NC in 67, and PD in 15, with a response rate of 35.9. The safety of the drug was assessed in 177, excluding ineligible patients and 3 who dropped out because of the concurrent use of other drugs. Adverse reactions were found in 93.2% of the patients, and abnormal values in clinical laboratory tests in 60.5%. Major unwanted symptoms included fever, nausea, vomiting, and anorexia. Major abnormal changes in laboratory tests were elevated total bilirubin and LDH and abnormal hepatic function. About half the patients had malaise and pain related to the intra-arterial infusion therapy. The one year survival rate was 56.9%, and the duration of survival of 50% of the patients was 407 days.

[Phase I clinical study of zinostatin stimalamer (YM 881) by intravenous injection]

A phase I clinical study by intravenous injection of zinostatin stimalamer (YM 881), a protein anti-cancer drug, was conducted in 50 patients with malignant tumors. The initial dose was 0.5 mg/m2 (n) in the single dose test, and 0.2 mg/m2/day in the repeated dose test for 5 successive days. Doses were increased up to 12n according to the modified Fibonacci's method in both the single and repeated dose tests. The dose limiting factor was thrombopenia in both the single and repeated dose tests. The maximum tolerated dose was 6.0 mg/m2 (12n) in the single dose test, and the subtoxic dose was 2.4 mg/m2/day in the five day repeated dose study. These results indicate that dose of 1.0 to 1.4 mg/m2/day (5 n to 7 n) are appropriate for the phase II repeated dose study.

[Early phase II study of YM 881 (zinostatin stimalamer) by intravenous injection. Research group for intravenous YM 881]

An early phase II multicentered study of YM 881 (zinostatin stimalamer) was conducted in 36 patients to investigate response and the safety of the drug in malignant tumors. The response could be evaluated in 18 patients, one with brain tumor, 2 with lung cancer, one with breast cancer, one with liver cancer, one with pancreatic cancer, 6 with gastric cancer, and 6 with colon cancer. PR was found in the patient with brain tumor. Major subjective unwanted effects were gastrointestinal symptoms. Objective evidence of hematological changes (thrombocytopenia, decreased hematocrit, and lymphocytopenia) was also obtained.

[Phase I study of YM881 (zinostatin stimalamer) suspension by hepatic arterial infusion. Research Group for Intra-arterial Infusion Therapy with YM881]

A phase I study of YM-881 (zinostatin stimalamer), neocarzinostatin combined with butylesterified styrene maleate, suspended in iodized poppy oil ethyl ester, was conducted in patients with hepatocellular carcinoma by giving single intra-arterial infusions via catheters inserted by Seldinger's method. Four dose levels, 2, 4, 6, and 8 mg, were tested. Major adverse reactions were fever, anorexia, nausea, vomiting, and abnormal hepatic function. Both the incidence and severity of adverse reactions tended to increase with the 8 mg dose. Tumor regression of 50% or more occurred in one receiving 2 mg and one receiving 4 mg. The results of the study suggest that doses of 6 mg or less may be appropriate for the phase II studies.