[Phase I study of a new antitumor antibiotic, neothramycin]

Phase I study of a new antitumor antibiotic, neothramycin which belongs to anthramycins was performed by a cooperative study group involving 15 major institutions. A total of 63 cases including 42 various solid tumors and 21 hematologic tumors refractory to standard treatments underwent the study during June 1979 to June 1981. Doses of single injection were escalated from an initial dose of 2 mg/m2 estimated by one twentieth of LD10 in mice up to 60 mg/m2. The most frequent and severest toxicity was nausea and vomiting seen in about the half of patients being administered dosages ranged from 24 mg/m2 to 40 mg/m2, and 3 out of 4 patients received dosages exceeding 50 mg/m2 required clinical managements; moreover, 1 out of 2 patients administered 60 mg/m2 was ranked as grade 4 of the criterion of toxicities in WHO handbook. Other clinical toxicities such as skin rash, hepatotoxicity or nephrotoxicity observed in the minority of the patients were reversible. Furthermore, hematologic toxicity was extremely mild and appeared not to be dose dependent. One patient with chronic myelogeneous leukemia had a hematological improvement and the other with esophageal cancer had a partial response. The result indicates that a dose limiting factor of neothramycin is nausea and vomiting, and a maximum tolerated dose of a single injection is 60 mg/m2. A dose schedule of 30-40 mg/m2 appears to be an optimal dose for Phase II study.

Correlation between the level of urinary D-glucaric acid and the degree of activation of masked compound (FT-207) in cancer patients

Phenobarbital stimulates the induction of liver microsomal drug-metabolizing enzyme, namely, cytochrome P-450, which enhances the rate of conversion of FT-207 to 5-FU, the active substance. When FT-207 is administered in combination with phenobarbital to cancer patients, the fluctuation in level of the drug-metabolizing enzyme, cytochrome P-450, should be taken into consideration. Therefore, it was investigated whether the urinary level of D-glucaric acid could be of value as an indicator for the evaluation of the activation of masked compounds, such as FT-207. The level of D-glucaric acid in urine was lower in cancer patients than in normal controls. The correlation between the level of urinary D-glucaric acid and that of 5-FU, which is an active metabolite of FT-207, in blood was statistically significant. The level of D-glucaric acid in urine was of use as an indicator for the evaluation of the activation of masked compounds, such as FT-207, in cancer chemotherapy.

Effects of inducer of liver drug-metabolizing enzyme on blood level of active metabolites of cyclophosphamide in rats and in cancer patients

It was already reported that a masked compound, cyclophosphamide (Endoxan, EX) undergoes the first step metabolism by a drug-metabolizing enzyme in liver microsomes, cytochrome P-450. By pretreatment with phenobarbital as an inducer of P-450, the maximum blood level of active metabolites of EX (normustard-like substances) in normal rats was 2.3 times higher than that in non-treated rats, in conformity with the increase in amount of liver P-450 and in alkylating activity of EX. In YS (Yoshida sarcoma)-bearing rats, the value of liver P-450 went down day by day to 1/2 on the 4th day after inoculation, but it remained normal when animals were pretreated with phenobarbital. In parallel with this, the blood level of normustard-like substances after EX administration was normal or showed a tendency toward increase. In 11 clinical cases pretreated with phenobarbital, the blood level of normustard-like substances 1 to 3 hr after EX administration, at the time when it reaches the peak was 1.5 times higher on an average than that in cases without pretreatment.

Studies on the mechanism of action of ACNU, 1-(4-amino-2-methylpyrimidine-5-yl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride: effects on cultured HeLa S3 cells

Treatment of cultured HeLa S3 cells with ACNU, 100 microgram/ml, for 30 min inhibited the cell growth intensely. The cell number was minimum on the 4th day after the treatment and recovered gradually, but it was still 24% of control of the 14th day. The colony formation, as an index of proliferation ability of cells, was remarkably inhibited and the number of colony formed on the 14th day after the treatment was 8% of control. DNA synthesis was inhibited by 59%, whereas little or no effect was observed on RNA or protein synthesis after 24 hr. Ethylene-14C-ACNU was bound to DNA and RNA to a similar degree, and that bound to the acid-insoluble fraction within 30 min was decreased by half after 24 hr and sustained thereafter. A significant decrease in sedimentation velocity of DNA on alkaline sucrose density gradient centrifugation was observed after 24 hr, and the decrease on neutral sucrose density gradient centrifugation was noticeable already by 2 hr. From the results of this study and other reports, the mechanism of action of ACNU seems to be alkalization of DNA followed by damage to DNA, which progresses quite slowly compared with other alkylating agents, causing cell damage and cell death.

Serum Zn content in tumor-bearing rats treated with anticancer drugs

The serum Zn content in rats bearing Yoshida-Sarcoma, AH 66F, AH 13 or AH 109A was found to be low as compared with that in normal controls. In the rats which had received intraperitoneal inoculum of Yoshida-Sarcoma, the effects of anticancer drugs were closely related to the changes in serum Zn content. Namely, serum Zn content increased and approached the normal range almost parallel with the prolongation of survival time by anticancer drugs. As the causes responsible for the reduction in quantity of serum Zn in the tumor-bearing rats, the reduction of serum albumin content and the accumulation of Zn in the tumor tissue and organs such as the liver and kidneys were suggested.

Combination chemotherapy for solid tumors using 5-fluorouracil, chromomycin-A, and prednisolone

Clinical effect of 5-fluorouracil or chromomycin-A3 alone, 5-fluorouracil + chromomycin-A3, and of the first two plus prednisolone on gastrointestinal and other solid tumors was evaluated. Out of 133 cases acceptable for evaluation, the number of responders was as follows: 3 (18.8%) of 6 cases treated with 5-fluorouracil alone, 1 (9.1%) of 11 cases treated with chromomycin-A3 or chromomycin-A3 hemisuccinate, 13 (21.7%) of 60 cases on the two-drug regimen, and 21 (45.7%) of 46 cases on the three-drug regimen. In cases of stomach carcinoma, response rate to the three-drug regimen was 54.2% (13/24), significantly higher than that of other regimens. At least 25% regression in the size of primary tumor was observed in 2 (7.1%) of 28 cases on the two-drug regimen and in 6 (33.3%) of 18 cases on the three-drug regimen. Of 51 cases on the three-drug regimen, steroid diabetes developed in 5 cases, moon face in 4 cases, and gastric ulcer in 1 case. However, toxic effect of these regimens (especially appearance of leucopenia) was less than those of previously tried combined regimens. The duration of response, on an average, was 10.8 weeks in 13 cases on the two-drug regimen and 11.7 weeks in 21 cases on the three-drug regimen. It was concluded from these results that a better response is obtained by the three-drug regimen than other regimens, and that prednisolone in combination, in addition to its favorable effect in improving the general condition of the patients, might enhance the anticancer effect of the drugs used in combination.