Brenda J. Foster

Chronic oral administration of CI-994: a phase 1 study.

Objectives: CI-994 (N-acetyl dinaline, PD123654) is a novel oral agent active in a broad variety ofmurine and human tumor xenografts. While cytotoxic in theBrown Norway (BN) rat leukemia model, growth inhibition inother murine and human tumor xenografts is predominantlycytostatic. Its specific mechanism of action remains unknown.Following CI-994 administration, inhibition of both histonedeacetylation and cellular proliferation at the G1 to Stransition phase of the cell cycle are observed. This Phase 1study in patients with solid tumors was carried out todetermine a maximum tolerated daily oral dose (MTD) for CI-994administered on a chronic basis. Methods: Fifty-threepatients received CI-994 daily for treatment durations rangingfrom 2 to 10 weeks. Dosage escalation proceeded in 2 phases;an Acute Dosing Phase (n = 11) to define the MTD for CI-994administered over 2 weeks and a Chronic Dosing Phase (n = 29)to define the MTD for daily administration for 8 weeks. Uponcompletion of the Chronic Dosing Phase, a third cohort ofpatients (n = 13) received CI-994 at the recommended Phase 2dose and schedule with 2 additional single doses of drugadministered separated by a 1-week washout to assess theeffect of food on CI-994 pharmacokinetics. Results:Thrombocytopenia was dose limiting at the MTD of 8mg/m2/day for 8 weeks. Other toxicities includedfatigue and gastrointestinal effects such as nausea, vomiting,diarrhea, constipation and mucositis. Pharmacokinetic studiesrevealed that peak plasma levels and AUCs generally increasedwith dose and that food intake did not affect the rate orextent of drug absorption. One patient with heavilypre-treated adenocarcinoma of the lung achieved a PartialResponse (PR) lasting over 2 years and 3 additional patientsachieved Stable Disease (SD), 1 each with non-small cell lung,colorectal, and renal cancer. Conclusions: Therecommended Phase 2 starting dose is 8 mg/m2/dayfor 8 weeks repeated after a 2-week drug-freeinterval.

Echinomycin: The first bifunctional intercalating agent in clinical trials

SummaryEchinomycin is a quinoxaline antibiotic that was originally isolated from Streptomyces echinatus. Based on its antitumor activity against two i.p. implanted murine tumors, the B16 melanoma, and the P388 leukemia, it was brought into clinical trials by the National Cancer Institute. Recent studies on its cytotoxic action have related its antitumor activity with its ability to bifunctionally intercalate with double stranded DNA.Toxicologic studies were carried out in CDF1 mice and beagle dogs using intravenous injections. For the mice studies the dose ranges were 288–692 mcg/kg (864–2076 mcg/m2) by single bolus, and 112–254 mcg/kg/day (336–762 mcg/m2/day) for five consecutive days. In the dog, dose ranges studied were 8.9–89.4 mcg/kg (178–1788 mcg/m2) by single bolus, and 3.4–33.5 mcg/kg/day (68–670 mcg/m2/day) for five consecutive days. The major toxic effects were found in the gastrointestinal, hepatic, and lymphoreticular systems. These were reversible at all but the highest dose, in dogs that had been treated for five consecutive days.Phase I clinical trials using various intravenous schedules were sponsored by the National Cancer Institute. Nausea, vomiting, reversible liver enzyme abnormalities, and allergic reactions were the most common toxicities encountered. Based on results from these studies, the National Cancer Institute has recently begun phase II trials in a broad range of diseases. These trials will further characterize echinomycins toxic effects and its antitumor activity.

Preclinical antitumor activity of CI-994

SummaryCI-994 [aka: acetyldinaline; PD 123654; 4-acetylamino-N-(2′aminophenyl)-benzamide] (Figure 1) is a novel antitumor agent with a unique mechanism of action. It is the acetylated metabolite of dinaline, a compound previously identified as having cytotoxic and cytostatic activity against several murine and human xenograft tumor models. CI-994 had activity against 8/8 solid tumors tested (log cell kills at the highest non-toxic dose): pancreatic ductal adenocarcinoma #02 (4.7); pancreatic adenocarcinoma#03 (3.0; 1/6 cures); colon adenocarcinoma #38 (1.6); colon adenocarcinoma #51/A (1.1); mammary adenocarcinoma #25 (1.7); mammary adenocarcinoma #17/ADR (0.5); Dunning osteogenic sarcoma (4.0); and the human prostate carcinoma LNCaP (1.2). CI-994 had the same spectrum of activity in vivo as dinaline. It also behaved similarly in schedule comparison/toxicity trials. Prolonged administration with lower drug doses was more effective than short-term therapy at higher individual doses. If doses were kept between 40 and 60 mg/kg/injection, prolonged administration (> 50 days) was tolerated with no gross toxicity. Doses ≥90 mg/kg/injection caused lethality after 4–5 days of administration. The maximum tolerated total dose was also increased with smaller individual doses administered for prolonged intervals. Clinical Phase I trials are ongoing with this agent.

Tumor Models and the Discovery and Secondary Evaluation of Solid Tumor Active Agents

AbstractEach independently arising tumor is a separate and unique biologic entity with its own unique histologic appearance, biologic behavior, and drug response profile. Thus, in drug discovery, no single tumor has been a perfect predictor for any other tumor. For this reason, new agents are evaluated in a variety of tumor models which is known as breadth of activity testing. In recent years, human tumors implanted in athymic nude mice and SCID mice have also become available for breadth of activity testing. In studies carried out in these laboratories, it was found that 10 human tumors metastasized in the SCID mice, but failed to metastasize in nude mice. In addition, tumor growth and tumor takes were superior in the SCID mice. The strengths and weaknesses of xenograft model systems are discussed. For example, most human tumor xenograft models are excessively sensitive to alkylating agents as well as to a new class of DNA binders (XE840 and XP315). Using human tumor models that are the least sensitive t...

Hexamethylmelamine: a critical review of an active drug.

Hexamethylmelamine is an s-triazine that began clinical trials during the 1960s based on its level of antitumor activity in murine tumor models. Phase I studies were performed using an oral formulation given in divided doses for varying numbers of days. The most frequently reported toxicities included nausea, vomiting, abdominal cramps, anorexia, weight loss and malaise. Less frequently reported toxicities were anemia, thrombocytopenia, leucopenia and peripheral neuropathy. Clinical antitumor activity was noted in the phase I studies in a variety of tumor types. Since then a large number of studies have been performed using hexamethylmelamine as a single agent and in a variety of combinations. Unfortunately, almost none of these studies sought to define the utility of this drug relative to other treatments for the diseases in which it showed activity, or to define the contribution of this drug to the activity of any given combination. Thus its role in the treatment of patients with malignancies remains undefined.

Phase I trial of Adozelesin using the treatment schedule of daily × 5 every 3 weeks

SummaryCC-1065 is a unique alkylating agent that preferentially binds in the minor groove of double-stranded DNA at adenine-thymine-rich sites. Although it has broad antitumor activity in preclinical models its development was discontinued because of deaths observed during preclinical toxicology studies. Adozelesin is a potent synthetic analog that was chosen for clinical development because it had a similar preclinical antitumor spectrum, but did not produce deaths similar to CC-1065 at therapeutic doses. Phase I evaluations using a variety of Adozelesin treatment schedules have been conducted. This report describes our experience using a multiple dose treatment schedule. Endpoints including antitumor response, maximum tolerated dose, dose limiting toxicity as well as other toxicities and the recommended Phase II starting dose were determined. Adozelesin was given as a 10 minute IV infusion for 5 consecutive days every 21 days or upon recovery from toxicity. The dose range evaluated was 6–30 mcg/m2/day. All patients had refractory solid tumors and had received prior cytotoxic treatment. Thirty-three patients (22 men: 11 women) were entered onto the study and 87 courses were initiated. Dose limiting toxicity was cumulative myelosuppression (leucopenia, thrombocytopenia). The maximum tolerated dose was 30 mcg/m2/day. The only other significant toxicity was an anaphylactoid syndrome that occurred in 2 patients. A partial response was observed in a patient with refractory soft tissue sarcoma. The recommended Phase II starting dose of Adozelesin using a 10 minute IV infusion for 5 consecutive days is 25 mcg/m2/day to be repeated every 4–6 weeks to allow recovery from myelotoxicity, based on our experience. Additional Phase I and II studies with Adozelesin are recommended.

Preclinical pharmacokinetic, antitumor and toxicity studies with CL-994 (N-acetyldinaline)

CI-994, a substituted benzamide derivative, is a compound that showed solid tumor selectivity for a variety of solid tumor models compared to L1210 leukemia. Due to its lack of aqueous solubility, it requires oral administration. Female B6D2F1 mice were treated with CI-994 once daily by oral administration of 50 mg/kg for 14 days. Following treatment mice were evaluated for pharmacodynamic effects as well as the pharmacokinetic behavior of CI-994 and the de-acetylated derivative dinaline. Mice samples (plasma, urine, feces) were analyzed using solid phase extraction, reverse phase HPLC and ultraviolet detection. The plasma distribution and elimination half-lives for CI-994 were 51 minutes and 9.4 hours, respectively, on D-1; 31 minutes and 3.4 hours, respectively on D-14. The apparent plasma distribution and elimination half-lives for dinaline were 27 minutes and 2.4 hours, respectively, on D-1; 40 minutes and 7.3 hours, respectively on D-14. The CI-994 AUC on D-1 and D-14 were 2879 and 2407 µ × minutes, respectively; while the dinaline AUC on D-1 and D-14 were 87 and 92 µg/ml × minutes, respectively. Urinary excretion for CI-994 and dinaline was higher on D-14, while the fecal excretion was the same on both days. The Colon #38 tumor growth in treated mice was reduced to 22% of that observed in the controls by D-19. The levels of all blood cells were reduced in the treated mice when compared to controls and the total WBC was the most affected (median 38%). Recovery to pretreatment levels occurred quickly following treatment cessation. Phase I evaluation of chronic oral administration of CI-994 is currently ongoing.

Identification and antitumor activity of a reduction product in the murine metabolism of pyrazoloacridine (NSC-366140)

Purpose. Pyrazoloacridine (PZA) is a newly developed anticancer agent currently undergoing clinical trials. Its mode of action has not been elucidated but the presence in its chemical structure of a 5-nitro functional group and its activity against oxygen-deficient cancerous cells argue in favor of enzymatic nitro reduction as a possible pathway for its antitumor activity. In order to assess the involvement of the nitro functiona lity in PZA activity, as well as to determine other metabolic products, a pharmacological and chemical study of PZA was designed. Methods. Urine and stool samples were collected from mice before and after treatment with PZA. Samples were fractionated using chromatographic methods and then evaluated using mass spectrometry (MS). One of the characterized metabolites was synthesized and tested in vitro and in vivo for anticancer activity. Results. One major fraction from mouse stool was initially characterized by MS as the 5-aminopyrazoloacridine (5-APZ). This compound was chemically synthesized by catalytic hydrogenation of PZA and stabilized as the hydrochloride salt. 5-APZ was marginally cytotoxic in vitro and was inactive in vivo against a tumor cured by PZA (Panc 03). Conclusions. Bioreduction of the nitro group to an amine compound from PZA represents a pathway in the metabolic sequence of PZA. The inactivity of the chemically generated amine product does not provide conclusive evidence that this pathway is not involved in the cytotoxicity of PZA because other intermediates in the nitro reduction pathway may have a role in the activity of PZA. In particular, the hydroxylamine derivative of PZA could give answers to the involvement of this pathway in PZA cytotoxicity.

Cryptophycin 1 cellular levels and effects in vitro using L1210 cells

Cryptophycin 1 is a natural product that was initially isolated from blue-green algae which has shown potent broad spectrum antitumor activity in preclinical in vitro and in vivo models. The drug strongly binds to tubulin and disrupts microtubule assembly for more than 24 hours after its removal. We evaluated cell survival, intracellular levels and inhibition of macromolecular synthesis in L1210 cells following exposure to cryptophycin 1 in vitro. Cell survival was strongly inhibited following drug exposure for either 1 or 4 hours. Intracellular drug levels were minimally affected by temperature (4°C versus 37°C) or exposure times up to 1 hour. However, extracellular drug concentration in culture media and increasing cell numbers did affect the concentration of intracellular drug levels in a nearly proportional manner. The synthesis of DNA and RNA was inhibited less than 5%, while protein synthesis inhibition was near 30%. Thus, none of the macromolecules were inhibited enough to explain the inhibition of tumor cell growth.