phase i clinical and pharmacokinetic trial of brequinar...

(CANCER RESEARCH 49. 4648-4653. August 15. 1989]

Phase I Clinical and Pharmacokinetic Trial of Brequinar Sodium(DUP 785; NSC 368390)1

Carlos L. Arteaga, Thomas D. Brown, John G. KÃ¼hn,Huey-Shin L. Shen, Timothy J. O'Rourke, Kenneth Beougher,H. James Brentzel, Daniel D. Von Hoff, and Geoffrey R. Weiss2

The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7884 [C. L. A., T. D. B., J. G. K., D. D. V. H., G. R. W.]; Brooke ArmyMedical Center, Fort Sam Houston, Texas 78234 [T. D. B., T. J. O., K. B.]; and DuPont Pharmaceuticals, Wilmington, Delaware 19898 [H-S. L. S., H. J. B.J

ABSTRACT

Brequinar sodium is a 4-quinolinecarboxylic acid analogue that inhibitsdihydroorotate dehydrogenase and subsequent tic novo pyrimidine biosynthesis. It has shown dose-dependent antineoplastic activity againstseveral mouse and human tumor models. This trial evaluated Brequinargiven as a single daily i.v. bolus over a 5-day period repeated every 28days. One hundred seven courses of treatment at dosages ranging from36 to 300 mg/nr/day x Â§were administered to 45 patients (31 male and14 female) with refractory solid tumors; median age was 58 years (range30-74); median Southwest Oncology Group performance status was 1(range, 0-3). Thirty patients had prior cytotoxic chemotherapy. Dose-limiting toxicities were thrombocytopenia and a severe desquamativemaculopapular dermatitis. Two of 5 good risk patients at 300 mg/m2 and3 of 6 poor risk patients at 170 mg/m2 developed a platelet count <25 xlO'Vpl. Two of 5 good risk patients at 300 mg/m2 and 1 of 6 poor riskpatients at 170 mg/m2 developed a severe desquamative dermatitis.

Moderate to severe mucositis was usually associated with the thrombocytopenia and/or the dermatitis. Nonhematological drug-related toxicitiesincluded nausea and vomiting, malaise, anorexia, diarrhea, phlebitis,reversible transaminase elevation, and mucositis. Other hematologicaltoxicities were anemia, granulocytopenia, and leukopenia. There were nodrug-related deaths. There were no objective tumor responses. Plasmaand urine levels of Brequinar were quantified by high pressure liquidchromatography in 28 patients. Plasma levels and areas under the curveincreased proportionally with increased dose. Brequinar had a harmonicmean terminal t,, of 8.1 Â±3.6 h with a model-independent determinedapparent volume of distribution at steady state of 9.0 Â±2.9 liters/m2 and

a total body clearance of 19.2 Â±7.7 ml/niin/nv. Renal excretion was aminor route of elimination for Brequinar. The maximally tolerated doseof Brequinar on a daily x 5 i.v. schedule was 250 mg/m2 for good risk

patients. For the daily x 5 i.v. schedule, the recommended dose ofBrequinar for phase II evaluation is 250 mg/m2 for good risk patientsand 135 mg/m2 for poor risk patients.

INTRODUCTION

Brequinar sodium or 6-fluoro-2-(2'-fluoro-l,l'-biphenyl-4-

yl)-3-methyl-4-quinoline carboxylic acid sodium salt (DUP785;NSC 368390) is a quinoline carboxylic acid analogue with broadpreclinical antitumor activity (Fig. 1). It has dose-dependentactivity against several mouse tumors in vivo (LI210 leukemia,P 388 leukemia, colon 38 carcinoma, and B16 melanoma) aswell as against several human xenografts (LX-1 lung, HCT-15colon, MX-1 breast, BL-STX-1 stomach, and CX-1 colon) (1).Few other established or investigational agents have exhibitedsignificant growth inhibition of the CX-1 and LX-1 xenografts(2). Additional preclinical data show that Brequinar inhibitslung mÃ©tastasesof B16 FIO melanoma in mice (3); in vitro, it

Received 10/11/88: revised 5/5/89; accepted 5/16/89.The costs of publication of this article were defrayed in part by the payment

of page charges. This article must therefore be hereby marked advertisement inaccordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1This work was supported by a grant from E. I. DuPont de Nemours, Inc..Wilmington. DE; General Clinical Research Grant RR-01346, NIH, DHHS; andthe clinical and support services of the Audie L. Murphy Memorial VeteransAdministration Hospital. San Antonio, TX. Presented in part at the AnnualMeeting of the American Society of Clinical Oncology in New Orleans. LA. May1988.

2To whom requests for reprints should be addressed.

inhibits growth of classic and variant small cell lung cancerlines (4). Brequinar is as potent as 5-fluorouracil and twice aspotent compared to 1-/3-Darabinofuranosylcytosine or metho-trexate against DLD-1 colon cancer cells in vitro (5).

Brequinar is an antimetabolite. Its mechanism of actionconsists of inhibition of dihydroorotate dehydrogenase andsubsequent disruption of de novo pyrimidine biosynthesis (6,7). This inhibition can be partially reversed in cultured humantumor cells by the addition of uridine or cytidine (6, 7). Preliminary in vitro and in vivo data indicate that a continuous presence of the drug is essential to maintain depletion of pyrimidinepools and subsequent tumor inhibition (8).

Preclinical toxicology animal studies showed that the majortarget organs for Brequinar were the gastrointestinal epitheliumand the bone marrow, with the gastrointestinal toxicity beingdose limiting.' When given i.v., venous destruction and phlebitis

were observed. At lethal doses in monkeys, moderate myocar-dial degeneration was found. Preclinical pharmacokineticsshowed high oral bioavailability in all species and high proteinbinding. Studies with radiolabeled drug indicated high levels ofBrequinar in intestinal tissues, liver, and kidney (9).

In light of the impressive preclinical antitumor efficacy ofBrequinar and its high water solubility (I), phase I clinical trialswith this drug were initiated. Because of the preclinical dataindicating a better antitumor effect with daily administrationof the drug (1,8), we chose to study Brequinar given as a singledaily i.v. infusion over a 5-day period. We now report themaximum tolerated dose, toxicity profile, pharmacokinetics,and antitumor effect of Brequinar in patients with refractorysolid tumors, when given with this schedule.

MATERIALS AND METHODS

Patient Selection

Patients with histologically documented, advanced, solid tumorsrefractory to all forms of known effective therapy were candidates forthis study. Other eligibility criteria included: (a) a life expectancy of atleast 8 weeks; (b) a Southwestern Oncology Group performance statusof 3 or less; (c) age >18 and <75 years; (d) a minimum of 3 weekssince prior chemotherapy and/or myelosuppressive radiotherapy; (e)adequate bone marrow function (absolute granulocyte count > 1900/pl,platelet count >130 x 10VM')-adequate liver function (normal biliru-bin), and a serum creatinine <2.0 mg/dl; and (/) no other coexistentmedical problems of sufficient severity to prevent full compliance withthe study. Patients who had previously received a cumulative dose of>400 mg/m2 doxorubicin were considered ineligible. All patients gave

written informed consent according to institutional and federal guidelines.

Drug Formulation and Administration

Brequinar sodium was supplied by Dupont Pharmaceuticals (Wilmington, DE) as a lyophilized powder in vials containing 100 or 500mg of active drug. Excipients included 40 mg each of sodium cholate

1Data on file at DuPont Pharmaceuticals: personal communication with Brian

K. Dallaire. Pharm.D.. Associate Director.

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PHASE 1 TRIAL OF BREQl'INAR SODILA)

Fig. I. Chemical structure of Brequinar sodium (DUP 785: NSC 368390).

and glycine in the 100-mg vials and 80 mg each in the 500-mg vials.The prescribed dose was diluted in 50-100 ml of 0.9% NaCl solutionand administered over 30 min through a peripheral i.v. line. The drugwas administered daily for 5 days on an inpatient basis.

Study Design

Prior to initiation of treatment with Brequinar, all patients had acomplete history and physical examination, hemogram, full chemistryprofile, urinalysis, chest roentgenogram, electrocardiogram, and a 24-h urine collection for creatinine clearance. Measurable tumor lesionswere documented with appropriate roentgenograms and computerizedtomographic scans.

The starting dose of Brequinar was 36 mg/m2 daily x 5. This dose

was escalated by 20-30% increments for each subsequent dose level.Treatment cycles were repeated every 28 days if there was no evidenceof disease progression and if toxicity was acceptable. At least threepatients were entered at each dose level. Dose escalation or deescalationfor individual patients was allowed.

Patients were seen weekly, with a history, physical examination, andthe routine laboratory studies noted above. Since myocardial necrosishad been observed in dogs,' patients were evaluated for the possibilityof cardiotoxicity. Starting at the 170 mg/m2 dose level, a follow-up

electrocardiogram was obtained on days 5 and 14 of each treatmentcycle. At and above this dosage, all patients had their pretreatment leftventricular ejection fraction determined by radionuclide scanning; thismeasurement was repeated every two cycles of treatment. Tumor measurements were performed at least every two cycles of treatment withSouthwest Oncology Group criteria used for response evaluation (10).

Toxicity was graded according to National Cancer Institute criteria(11). Dose-limiting toxicity was defined as toxicity of grade 3 or higherobserved in at least 2 patients at a given dose level. The maximumtolerated dose was defined as the dosage immediately below that atwhich dose-limiting toxicities occurred.

In order to determine if the toxicity profile of Brequinar varieddepending on the extent of prior treatment, patients at the 170 mg/m2

dose level were prospectively divided into good and poor risk groups.Poor risk patients were those with: (a) prior treatment with nitrosoureasor mitomycin C; (b) prior radiotherapy to Â£30%of their bone marrow;and/or (c) prior high dose chemotherapy requiring autologous bonemarrow rescue.

Pharmacokinetic Study

Blood Sampling and Urine Collection. Preinfusion and end-of-infu-sion 8-mI blood samples were collected on days 1 through 5 of patients'

first cycles from an indwelling i.v. heparin lock in the arm contralateralto the infusion line. Additionally on days 1 and 5, samples werecollected 15, 30, and 60 min, and 2, 4, 6, 8, 12, 14, 16, 20, and 24 hpostinfusion. The samples were separated by cold centrifugation andthe plasma was flash frozen in acetone-dry ice. Urine was collectedprior to drug administration, from 0 to 12 h and 12 to 24 h on day 1,and every 24 h for 5 days. The total volume was recorded and a 20-mIaliquot of urine was removed. Plasma and urine samples were stored atâ€”20Â°Cin polyethylene tubes until further analysis.

High Pressure Liquid Chromatography Analysis. Brequinar concentrations in plasma and urine were measured by high pressure liquidchromatography. Internal standards (DuPont compounds S-6056 forplasma and DUP416 for urine) were added to each plasma/urine sampleprior to extraction. Spiked urine and plasma standard curves wereprepared on the day of each procedure. Tetrabutylammonium hydrox

ide (4 HIM,500 dl ) was added to 1 ml of plasma or urine and extractedwith 10 ml of mÃ©thylÃ¨nechloride. After shaking (Eberbach Corp., AnnArbor, MI) of the mixture for 30 min and centrifugation at 2000 rpmfor 10 min, the dichloromethane layer was removed and evaporated todryness under a gentle stream of nitrogen. The extraction yield for bothdrug and internal standard averaged 89% from plasma and 100% fromurine. Samples were reconstituted with 200 p\ of mobile phase:CH,CN:H;O:0.1 M H,PO4, 55:25:20 (60:20:20 for urine). Ten ^1 ofsample were then injected (WISP model 71OB autosampler; WatersAssociates, Milford, MA) onto a 4.6-mm x 25-cm Zorbax CÂ»(urine)or a 4.6-mm x 25-cm Biophase Octyl (plasma) column, with the mobilephase pumped (model SP 8700; Spectraphysics, San Jose, CA) at aflow rate of l ml/min. UV absorbance (model 441; Waters, Milford,MA) was monitored at 254 nm. Chromatograms and peak height ratioswere stored and analyzed on a Hewlett Packard HP9816 Computer(Hewlett Packard, Palo Alto, CA). Retention times for Brequinar andDUP416 were 8.8 and 10 min, respectively, with the lower limit ofsensitivity of the assay set at 25 ng/ml. The intraday coefficient ofvariation was less than 9% over the linear range (25 ng/ml to 20 Mg/ml) of the plasma assay and between 0.2% (10 Mg/ml) and 10.2% (50ng/ml) for the urine assay. For spiked plasma samples, the interdaycoefficient of variation ranged from 2.5% to 9.4% (five experiments)and from 0.6% to 4.2% (five experiments) for spiked urine samples.Stability of Brequinar in blind-coded spiked plasma and urine samplesstored frozen at -20Â°Cwas determined at various intervals for 1 year.

Brequinar was stable in frozen plasma and urine for at least 1 year.Pharmacokinetic Analysis. Analysis of the pharmacokinetic data was

performed by noncompartmental methods (12). Pharmacokinetic parameters were determined from day 1 plasma data. Total plasmaclearance (CL), apparent volume of distribution (K/â€žâ€ž),and volume ofdistribution at steady state (K/J were calculated according to thefollowing:

CL = Dose/AUC DoseAUC-X

V... =Dose-AUMC Dose-T

(AUC)2 2-AUC

where T is the infusion time and represents the first-order eliminationrate constant. The area under the plasma concentration-time curve(AUC) was estimated by the linear trapezoidal method up to the lastmeasurable data point and extrapolated to infinity (AUC,,.Â»).The areaunder the first moment curve (AUMC) was calculated according to thefollowing equation:

AUMC = AUMC, + â€” + â€”2A A"

where C is the drug concentration at the last sampling time, i. Theplasma terminal half-life (i./.)was calculated by 0.693/X.

RESULTS

Forty-five patients were entered in this trial. Patient characteristics are shown in Table 1. The median performance statuswas 1, with only 8 of 45 patients having a performance statusof >2. Thirty patients had received prior chemotherapy. Patients with non-small cell lung or colorectal cancer represented69% of the patients treated. A total of 107 courses of Brequinarwere administered. Two patients received an incomplete coursebecause of cancer-related complications during treatment. Twoadditional courses were inevaluable because of dosage errors.Patients received a median of 2 cycles of treatment (range, 1-10), with only 5 patients receiving 5 or more cycles. There werea total of 3 deaths in the study, all disease related: one patientwith Staphylococcus aureus sepsis complicating metastaticsquamous cell carcinoma of the lung, one patient with smallbowel obstruction and Gram-negative sepsis secondary to in-traabdominal mÃ©tastasesfrom a non-small cell lung cancer, and

4649



PHASE I TRIAL OF BREQUINAR SODIUM

Table 1 Patient characteristics

TotalMale/femaleMedian

age(range)MedianSouthwestern OncologyGroupperformance

status(range)Prior

treatmentNoneRadiation

onlyImmunotherapyonlyChemotherapyonlyRadiation

+chemotherapyTumor

typesLung(non-smallcell)ColorectalRenal

cellProstateBreastStomachMelanomaAdenocarcinoma

unknownprimaryLymphoma45

(107courses)31/1458

(30-74)1(0-3)672181216155321111

Table 2 Dose escalations ofBrequinar

Dose(mg/m1)36486485110135'170-210250300No.

ofpatients36567711365No.

of Ã©valuablecourses761081011175217

" Patients stratified into good and poor risk groups.

a third patient with bronchial obstruction and postobstructivepneumonia secondary to a large cell carcinoma of the lung.

Dose escalations are shown in Table 2. At the 135- and 170-mg/m2 dose levels, 1 of 7 and 6 of 11 patients, respectively,

were in the poor risk group.Toxicity. Side effects of Brequinar were hematological and

nonhematological. The nonhematological toxicities are summarized in Table 3. The dose-limiting nonhematological tox-icity was dermatitis, which developed in 6 of the 7 courses at300 mg/nr and was usually associated with moderate mucositis.In 2 instances the dermatitis was a severe painful maculopapularrash involving the face, neck, upper trunk, upper arms, and theinguinoperineal area. It was associated with diffuse desquamation in 1 case and with scrotal sloughing in the other. In bothcases, skin biopsies revealed a nonspecific mononuclear infÃltrate. On empiric systemic steroids, the rash subsided within

7-10 days in both instances. In one poor risk patient treatedwith 170 mg/m2, a desquamative rash of slightly less severity

involving the inguinoperineal and scrotal areas was observed.In other instances the rash was mild and asymptomatic, appearing mostly in areas of skin contact (i.e.. cardiac monitorpatches, waist bands, etc). In the only patient with dermatitisthat was rechallenged with drug, this mild rash did not worsen.In another patient is persisted for 3 months after discontinuation of drug treatment.

Nausea and vomiting were easily controlled with conventional doses of phenothiazines. Reversible elevation of liverenzymes (serum glutamic oxalacetic transaminase and serumglutamic-pyruvic transaminase occurred in a total of 6 coursesby day 7 (median) and returned to normal by day 21 (median).In only 1 patient was this elevation associated with liver dysfunction, as evidenced by a marked rise and rapid decline inserum bilirubin. Phlebitis, characterized by burning at the injection site, was easily controlled by increasing the volume ofthe infÃºsatefrom 50 to 100 ml. Diarrhea was mild to moderateand reversible, with only 1 patient requiring i.v. hydration.Mucositis was clearly dose related and was worse in patientswith extensive prior therapy. The two episodes of grade 3mucositis, all at 170 mg/m2, occurred in poor risk patients. In

good risk patients, mucositis was grade 2 or less. Although notdose-limiting, diarrhea and phlebitis were also dose related(Table 3).

No cardiotoxicity was observed in this trial.Hematological toxicities are summarized in Table 4. Throm-

bocytopenia was the dose-limiting myelosuppressive toxicitydeveloping at median day 8 (range, days 4-18) and consistentlyresolving by day 28 (>130 x 10VM')- In 2 patients a bonemarrow aspirate and biopsy at the time of hematological nadirshowed decreased cellularity and reduced number of megakar-yocytes, confirming the myelosuppressive effect of Brequinar.No bleeding complications occurred. Although 10 of 21 coursesat 250 mg/ml2 were associated with thrombocytopenia, none ofthese was associated with a nadir platelet count <50 x 1O-'/AII-

Two patients have each received 7 and 9 courses of treatmentat this dose level. Mild thrombocytopenia (grade 1) was observed in 6 of 7 cycles in the first patient, suggesting nocumulative myelosuppression. The second patient has not exhibited any toxicity.

The few episodes of anemia were associated with a lowreticulocyte count and resolved by day 21. No patient requiredblood transfusions. Granulocytopenia and leucopenia wereclearly dose related but not dose limiting. When present, theywere always associated with thrombocytopenia.

As shown in Table 3, the majority of the toxic courses at 170

Table 3 Courses ofBrequinar associated with nonhematological toxicity

No. of toxic courses (grades1-4)Dose

Total no.(mg/m2) ofcourses48

6485

1101351702102503006

108

101117

521

7Nausea

andvomiting1

2133ri34Malaise

andanorexia1

013

33

223Hepatotoxicity1

01004Â»

000Phlebitis0

11

267235Diarrhea0

01

101023Mucositis0

00015'

134Dermatitis0

0010f0

06"

4 of 7 poor risk.* 3 of 4 poor risk.' 3 of 5 poor risk.â€¢*1 of 1 poor risk.

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Table 4 Courses of Brequinar associated with hematological toxicity

Dose(mg/m2)64135170210250300ofcourses101117S217No.

of toxic courses (grades1-4)Anemia"021002Granulocytopenia*01

(1)'3/(l)003

(1)Leukopeniar016*0)016 (1)Thrombocytopenia*'25

(1)7*(4)1105

(3)Â°Hemoglobin, <11 g/dl.* Polymorphonuclear cells, <1900/VI.r WBC, <4500/^l.''Platelets. < 130 x lO'/xl.' Numbers in parentheses, no. of courses with grade ^3 toxicity. At 170 mg/m2, 5 of 6 courses associated with grade ^3 myelosuppression occurred in poor risk

patients./l of 3 poor risk."2 of 6 poor risk.A3 of 7 poor risk.

mg/m2 were observed in poor risk patients. At this same dosage,

5 of 6 courses associated with grade 3 or 4 myelosuppressionoccurred in poor risk patients (Table 4), suggesting an adverseeffect of extensive prior therapy on patient tolerance to Brequinar.

Table 5 summarizes the dose-limiting toxicities in this study.Two of 5 good risk patients at 300 mg/m2 and 3 of 6 poor riskpatients at 170 mg/m2 developed a platelet count <25 x IO1n\.Two of 5 good risk patients at 300 mg/m2 and 1 of 6 poor riskpatients at 170 mg/m2 developed a severe desquamative der

matitis.Antitumor Activity. There were no objective tumor responses

to Brequinar when it was given as a daily i.v. bolus over a 5-day period.

Pharmacokinetics. Plasma and urine concentrations of Brequinar were quantified by high pressure liquid chromatographyin 28 patients. Peak plasma concentrations on days 1 and 5 atdoses ranging from 135 to 300 mg/m2 are shown in Table 6.

Median peak plasma levels did not change appreciably from

Table 5 Dose-limiting toxicities of Brequinar

Dose(mg/m2)135

170300No.

ofpatients7

115ThrombocytopeniaGrade

3Â°Ie1Grade 4*0y2DermatitisGrade30j

(0Grade

40

02

" National Cancer Institute toxicity criteria; >25-49 x I0'/>il.*<25x 103M' Poor risk patients.

Table 6 Peak plasma concentrations of Brequinar at or near the recommendedphase II dose (250 mg/m'/day x 5)

Patientno.19

202122

242630

313233

3537

38Dose(mg/m2)135

135135170

170170210

210210250

250300

300Time"

(h)0.08

0.000.000.00

0.000.000.08

0.080.000.02

0.050.02

0.00Day

1Concentration

Gig/ml)35.60

40.2435.2137.19

59.6949.0953.19

67.6052.8475.22

62.2698.99

82.69Time

(h)0.50

0.000.080.00

0.000.000.00

0.17NA*0.00

0.080.00

0.00Day

5Concentration

Gig/ml)27.39

49.6655.3832.17

49.7547.5360.98

57.90NA81.43

62.1498.29

98.04" Sample time postinfusion.4 NA, not available.

day 1 to day 5. However, median trough levels increased from0.68 Â¿ig/mlon day 1 to 1.43 ng/m\ on day 5 (data not shown).A typical plasma concentration-time curve for days 1 and 5 isshown in Fig. 2.

The pharmacokinetic parameters derived from the data obtained on day 1 in all 28 patients are presented in Table 7.Although large interpatient variability was observed, AUCsincreased proportionally with increasing doses of Brequinar (r= 0.85). Brequinar had a harmonic mean terminal tv, of 8.1 Â±3.6 h with an apparent volume of distribution of 15.5 Â±6.0liters/m2. The apparent steady state volume of distribution was9.0 Â±2.9 liters/m2. The mean plasma clearance was 19.2 Â±7.7ml/min/m2. The percentage of the total dose that was excretedunchanged in the urine in a 24-h period varied between 0.13%and 5.5%. To assess pharmacokinetic linearity during the 5-day treatment, day 1 AUC was then compared with day 5 AUC.AUCs increased from day 1 to day 5 by only a mean of 23%(range, â€”1to 42%). Interestingly, the percentage of change in

the pretreatment platelet count induced by Brequinar treatmentcorrelated well with the day 1 AUC (P< 0.002; Spearman ranktest) (Fig. 3). The observed decrease in platelet count did notcorrelate with peak plasma drug levels (data not shown).

DISCUSSION

We have evaluated Brequinar sodium, an inhibitor of de novopyrimidine biosynthesis, in a phase I clinical and pharmacokinetic trial of a daily i.v. bolus injection over a 5-day period.Preclinical studies have shown a maximum tolerated dose of 6mg/mg2 i.v. daily x 5 in dogs.' According to current practice

in phase I clinical trials with anticancer drugs, the starting dosein humans should have been one third ofthat (13) or 2 mg/m2.

However, at the time of initiation of this trial, doses of 100mg/m2 i.v. daily x 5 had been safely administered to patients

with advanced cancer and minimal prior treatment (14). Basedon this preliminary information, an initial dose of 36 mg/m2

i.v. daily x 5 was chosen.The dose-limiting toxicities in this trial were thrombocyto-

penia and a severe maculopapular desquamative dermatitis,usually associated with moderate to severe mucositis. Thesefindings are consistent with the preclinical toxicology studies,which showed that the major target organs of toxicity in allspecies tested were the gastrointestinal epithelium and the bonemarrow.1 Accordingly, diarrhea, leucopenia, and granulocyto-

penia were also observed in this trial and, although not doselimiting, they were clearly related to dose (Tables 3 and 4).Similar to other inhibitors of de novo pyrimidine biosynthesissuch as ^-(phosphonacetylJ-L-aspartic acid (PALA) and pyra-

4651



Fig. 2. Postinfusion Brequinar plasma concentrations, days 1 (O) and 5 (â€¢),in patient 37treated with 300 mg/m2/day x 5.


H ^

TIME(hp)

Table 7 Pharmacokinetic parameters of Brequinar

Dose(mg/m2)36486485110135170210250300Mean

(28patients)SDNo.

ofpatients3343332322Day

1AUCo-."

(/jg-h/ml)25.3839.71114.8195.5688.11103.53123.83258.82216.10714.37Day

5AUCo^h(iig-h/ml)26.8141.4698.92130.80114.00143.23151.19309.85301.60919.02Mn)8.28.67.97.85.77.38.18.39.519.58.09*3.6CL(ml/min/m2)23.9224.6015.4217.3522.2522.4024.5714.6619.327.7019.197.7P*-(liters/nr)18.2219.6610.9413.5312.4814.2722.1512.3015.9812.7915.546.0^,,(liters/nr)9.4311.467.348.597.488.0612.968.388.789.088.972.9

Â°AUC, area under the plasma concentration-time curve; !â€¢â€ž,plasma terminal half-life; CL, total plasma clearance;

volume of distribution at steady state." Harmonic mean.

â€ž,apparent volume of distribution;

TOOOn

800

6OO-

400

200H

r - 0 64p < 0.002

O 20 40 60 80 100

Platelet Count (% change)

Fig. 3. Correlation between day 1 AUC and the observed percentage of changein the pretreatment platelet count induced by Brequinar. Day 1 AUC wasestimated as described in "Materials and Methods." Statistical analysis was done

with the Spearman rank test (28 patients).

/oturan (15, 16), dermatitis was observed in 2 of 5 good riskpatients at 300 mg/nr and in 1 of 6 poor risk patients at 170mg/nr (Table 5). Although the pathogenesis of this toxicmanifestation is unknown, its occurrence raises the possibilitythat regeneration of the skin might be highly dependent uponde novo pyrimidine biosynthesis. Preclinical studies did notshow any accumulation of radioactive Brequinar in the skin oftest animals.1 A similar Brequinar-induced toxic dermatitis has

recently been reported by Schwartsmann et al. (17).

Extensive prior treatment decreased the tolerance to thehigher doses of Brequinar. At 170 mg/nr, we prospectivelydivided our patient population into good and poor risk groups.Four of 6 poor risk patients at this dose level developed unacceptable toxicity: grade 4 thrombocytopenia with moderate tosevere mucositis (3 patients) and a severe rash (1 patient). Othernonhematological toxicities were also more evident in the poorrisk group. The majority of courses associated with nausea andvomiting, hepatotoxicity, and mucositis occurred in poor riskpatients (Table 3), further indicating a biological impact ofextensive prior therapy on subsequent patient tolerance toBrequinar.

Since few patients received multiple courses of treatment atthe maximum tolerated dose, cumulative toxicity with Brequinar cannot be addressed by this trial. Furthermore, all theinstances of dose-limiting toxicity occurred during the first cycleof treatment and, therefore, cannot be considered to be due tocumulative drug effects. Only 2 patients received 7 and 9 coursesof treatment each (250 mg/nr) with minimal myelosuppressionoccurring in only the first one.

No objective responses were observed in this trial. However,the limited number of patients and tumor types entered at thehigher doses precludes any conclusion as to the antitumorefficacy of Brequinar. Since recent preclinical data indicate thata continuous presence of the drug is more effective in depletingpyrimidine pools (8), and given the pharmacokinetic profile of

4652



PHASE l TRIAL OF BREQUINAR SODIUM

Brequinar (see below), it is conceivable that a continuous infusion of this agent might be more effective in achieving anantitumor effect. Furthermore, since depletion of pyrimidinepools enhances the metabolism of 5-fluorouracil ( 18), Brequinar

may enhance the antitumor activity of other antimetabolites.Further studies are necessary to address these possibilities.

The pharmacokinetic data showed that the plasma disposition of Brequinar followed a biexponential pattern, with aharmonic mean terminal half-life of 8.1 h. Large interpatient

variability was observed, but AUCs correlated well with thedose of Brequinar and with the observed percentage of changein the pretreatment platelet count. There was a mean 23%increase in day 5 AUC compared to day 1 AUC, suggesting asmall decrease of drug clearance over the 5-day treatmentperiod. In agreement with animal pharmacokinetic data,1 renal

excretion of Brequinar was minimal. At dosages up to 250 mg/nr/day x 5, our recommended dose for phase II clinical trials,the pharmacokinetic parameters were clearly independent ofdose (Table 7). The mean plasma clearance and terminal t,, at300 mg/nr (2 patients) suggest that pharmacokinetics mightbecome nonlinear at higher doses. Due to the limited numberof patients with severe toxicity and concurrent pharmacokineticdeterminations, we cannot correlate further the severity of theside effects with any potentially predictive pharmacokineticparameter.

Based on the results of this study, the recommended phase IIdose of Brequinar given i.v. daily x 5 is 250 mg/m2 for goodrisk patients and 135 mg/m2 for poor risk patients. It is possible

that, in the absence of toxicity at 250 mg/nr, some patientsmay tolerate higher doses of Brequinar. However, because of:(a) the lack of cumulative toxicity data; (b) the pharmacokineticdata suggesting nonlinearity at doses higher than >250 mg/m2;

and (c) the unpredictable and severe toxicity we observed at300 mg/m2 in patients with good performance status and no

significant prior treatment, escalating Brequinar above 250 mg/m2 daily x 5 cannot be recommended.

ACKNOWLEDGMENTS

The nursing and dietetic care provided by the staff at the AudieMurphy Veterans Hospital Special Diagnostic and Treatment Unit isappreciated. We wish to thank Heidi Herndon, R.N., Robbie Fuqua,Nancy Pullin, and Shirley McVea, R.N., for their assistance in datamanagement.

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1989;49:4648-4653. Cancer Res Carlos L. Arteaga, Thomas D. Brown, John G. Kuhn, et al. (DUP 785; NSC 368390)Phase I Clinical and Pharmacokinetic Trial of Brequinar Sodium

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