Preclinical toxicology study of liposome encapsulated doxorubicin (TLC D-99) given intraperitoneally to dogs.

A preclinical toxicology study of intraperitoneally administered liposome encapsulated doxorubicin and free doxorubicin was carried out in beagle dogs. Dogs received single intraperitoneal infusions of 1.5 mg free or 1.5, 2.25 or 3.37 mg liposomal doxorubicin/kg. One group of four dogs received 1.5 mg liposomal doxorubicin/kg every three weeks for 4 cycles. The dose limiting toxicity of free or liposomal doxorubicin given by the intraperitoneal route was a dose-related chemical peritonitis. This toxicity was more severe in dogs that received by the intraperitoneal route the previously determined maximally tolerated intravenous dose of liposomal doxorubicin (2.25 mg/kg). The abdominal toxicity was characterized by capsular fibrosis and ascites formation. Abdominal toxicity was life threatening after single doses of 3.37 mg liposomal doxorubicin kg, or after multiple (4) doses of 1.5 mg liposomal doxorubicin/kg. Thoracic toxicity (increased fluid, mediastinal edema, thickening of the parietal pleura) was seen after multiple (every 3 weeks for 4 cycles) intraperitoneal doses of 1.5 mg or single doses of 3.37 mg liposomal doxorubicin/kg. Myelosuppression was seen in all groups, but was less severe after intraperitoneal dosage than after intravenous dosage of liposomal doxorubicin.

Liposome encapsulated vincristine: preclinical toxicologic and pharmacologic comparison with free vincristine and empty liposomes in mice, rats and dogs.

A preclinical toxicology study of liposome encapsulated vincristine, free vincristine and empty liposomes was carried out in mice and dogs by single and multiple (daily for 5 days) intravenous injection. Single and multiple dose intravenous injection studies in mice showed the encapsulated form of vincristine to be less toxic than free vincristine. Empty liposomes injected intravenously into dogs were without significant toxicity. In dogs, the toxicities seen with liposomal vincristine were qualitatively similar to those of free vincristine with only minor quantitative differences. The principal toxicities of free and liposomal vincristine in dogs were anorexia, weight loss, pyrexia, myelosuppression and gastrointestinal toxicity. After single high doses of either formulation gastrointestinal toxicity was the dose-limiting toxicity, while either hematologic or gastrointestinal toxicity was dose limiting after multiple dose administration of either drug. Histopathologic lesions of importance were bone marrow atrophy, necrosis and atrophy of the lymphoproliferative tissues, necrosis of gastrointestinal tract mucosa, liver and pancreas, and hemorrhage. Distribution studies in rats showed significantly higher vincristine levels in serum, spleen, liver, trachea, jejunum, cerebrum, lung, ischiatic nerve and heart, and significantly lower levels in colon, stomach, salivary gland, thymus esophagus and pancreas after injection of the liposome-associated agent. No toxicities were seen that should preclude safe clinical trial of liposomal vincristine in man.

Preclinical toxicologic evaluation of DENSPM (N1,N11-diethylnorspermine) in rats and dogs.

A toxicology study of DENSPM was carried out in rats by multiple (once daily for 5 days) intravenous injection. Doses of 12.5, 25 and 50 mg DENSPM/kg were well tolerated. Infusion of 100 mg DENSPM resulted in distressing physical signs, including labored breathing, convulsive movements and acute death. There were no end-organ toxicities induced by this regimen as evaluated by serum chemistry and hematology examinations, and histopathologic exam of all major body organs. Transient hypotension was induced in rats and dogs by rapid infusion of DENSPM; the magnitude of this hypotension was decreased by slow infusion of DENSPM into dogs. Hypotension appears to be the dose-limiting toxicity of this agent when infused rapidly.

Comparison of the cardiotoxic effects of liposomal doxorubicin (TLC D-99) versus free doxorubicin in beagle dogs.

The cardiotoxic potential of liposome encapsulated doxorubicin (TLC D-99) prepared by a remote-loading technique was compared with that of free doxorubicin (1.5mg/kg administered every 3 weeks for 8 cycles) in beagle dogs. Both agents were equally myelosuppressive, and all dogs completed both treatments. There were no deaths during the study. Experimental animals were killed between 157 and 164 days after the start of the trial. All of the dogs (n = 6) that received free doxorubicin had either moderate (1 animal) or severe (5 animals) vacuolization of myocardial tissue. None of the dogs treated with liposomal doxorubicin had lesions suggestive of cardiomyopathy. Administration of free doxorubicin was associated with transient anorexia, reduced weight gain, alopecia, and gastrointestinal toxicity. Such adverse reactions were either much less severe or absent in animals that received liposomal doxorubicin. The results of this study demonstrate that TLC D-99 significantly decreases both the myocardial toxicity and other adverse reactions of this potent antineoplastic drug. TLC D-99 is now in Phase II clinical trials.

Preclinical toxicology study of liposome encapsulated doxorubicin (TLC D-99): comparison with doxorubicin and empty liposomes in mice and dogs.

A preclinical toxicology study of intravenously administered liposome encapsulated doxorubicin (TLC D-99), free doxorubicin and empty liposomes was carried out in mice and dogs by single and multiple (daily for 5 days) dose schedules. Single dose intravenous injection studies in mice showed the encapsulated form of doxorubicin to be less toxic (LD50 of 32 mg/kg) than free doxorubicin (LD50 of 17 mg/kg). Toxicity in dogs was evaluated by serial serum chemistry, hematology and EKG analysis, urinalysis, clinical observations, necropsy and histopathologic examination. Empty liposomes injected intravenously into dogs were without significant toxicity. The maximally tolerated dose of free doxorubicin in beagles was 1.5 mg/kg; deaths were seen after a 50% escalation to 2.25 mg/kg. The maximally tolerated dose of liposome encapsulated doxorubicin was higher (2.25 mg/kg); deaths were seen after a 50% escalation to 3.37 mg/kg. A toxicity unique to the encapsulated agent was pyexia (as high as 105.6 degrees F) within twenty four hr of single dosage. This was seen in approximately half of the test animals, was not dose-related, and was not observed in animals that received empty liposomes. The organ specific toxicities seen with TLC D-99 were qualitatively similar to those of free doxorubicin, but less severe.

Prostatic atrophy in dogs after intravenous administration of a ureido-ethylimidazoline derivative (CGP15'720A).

1-(2-[4-Pridyl)-2-imidazoline-1-yl]-ethyl)-3-(4-carboxyphenyl)urea (CGP15'720A) is an experimental antineoplastic agent with marked activity against carcinogen-induced lung tumors in Syrian hamsters and human lung tumor xenografts in nude mice. A preclinical toxicity study of this agent was carried out in mice and dogs which demonstrated the relatively nontoxic nature of the agent. In mice, single intraperitoneal dosage of 12 g/m2 did not produce lethality; however, lethality (30% of treated mice) was seen during treatment with 6 g/m2 daily for 5 days. No hematological, serum-chemistry or histopathological changes were detected in mice after single or five consecutive treatments with 12 g/m2. Dogs were treated with doses ranging from 5 g/m2 to 80 g/m2, with deaths occurring in a non-dose-related fashion after 10, 20, and 40 g/m2. Acute neurological toxicity after infusion was the dose-limiting toxicity in dogs. There were no consistent hematological or serum-chemistry aberrations in the treated dogs. The most consistent histopathological finding was prostatic atrophy, which was detected in 5/12 dogs in this series.

Preclinical toxicity study of streptozocin infused into the internal carotid artery of dogs and baboons.

Mature male and female dogs (10) and male baboons (4) were each given a single dose of streptozocin (STZ) (1000 mg/m2) by infusion directly into the left internal carotid artery over a two-hour time period. Serial hematology and serum chemistry profiles and physical observations were made, the animals necropsied at varying times after dosage, and the major organs examined histologically. In dogs, severe weight loss, neutrophilia, electrolyte disturbances, decreased liver function, diabetes and decreased serum amylase levels were the major toxicities. In baboons, weight loss, hypoglycemic coma, diabetes, decreased liver function and electrolyte disturbances were observed. While systemic toxicities were severe in both animal species, central nervous system toxicity was minimal. Cerebral toxicities consisting of edema in two dogs, and focal necrosis in one dog were observed histopathologically. No cerebral toxicity occurred in baboons. Based upon these findings, a phase I clinical trial of intra-arterial (internal carotid artery) STZ in patients with primary/metastatic brain tumors would appear feasible.

Preclinical toxicity study of mitomycin C infused into the internal carotid artery of beagle dogs.

Young adult male and female beagle dogs were infused with single doses of 0.5 (2 dogs) or 0.25 mg (5 dogs) Mitomycin C (MMC)/kg body weight directly into the internal carotid artery. Serial hematology and serum chemistry profiles, electrocardiograms and physical observations were made, the animals necropsied at varying times after dosage, and the major organs examined histologically. Results indicate that the dose limiting toxicity of this treatment regimen is myelosuppression. No ocular or neurologic toxicity was detected in any test animal. The findings suggest that infusion of MMC can be safely attempted in humans for the treatment of brain tumors that derive their blood supply from the internal carotid artery.

Some short-chain N6-substituted adenosine analogues with antitumor properties.

The compounds N6-allyl-, N6-isopropyl-, N6-propargyl-, and N6-(2-methylallyl)adenosine were prepared by reacting 6-chloropurine riboside with an excess of the corresponding amines in ethanol, in the presence of two acid acceptors resulting in virtually quantitative yields. The compounds showed biological activity in a number of in vitro and in vivo tumor cell systems. Very good increases in life spans of mice bearing mammary carcinoma were obtained by treatment with the N6-allyl, N6-isopropyl, and N6-propargyl analogues, respectively. In rats, the N6-allyl analogue slowed the rate of transplantable mammary tumor growth by one-fourth. The short-chain adenosine analogues are more active in the treatment of animal carcinomas than in the leukemia or sarcoma tumor cell systems.