Investigational New Drugs9: 41-47, 1991. 9 1991KluwerAcademicPublishers. Printedin the Netherlands.

Crisnatol mesylate: Phase I dose escalation by extending infusion duration Elizabeth A. Poplin 1, Guy G. Chabot 2, Richard L. Tuttle 3, Sol Lucas 3, William A. Wargin 3 and Laurence H. Baker 1 1Department of Internal Medicine, Division of Hematology and Oncology, Wayne State University School of Medicine, Detroit, Michigan 48202-0188, USA; 2Institute Gustav-Roussy, Pavillon De Recherche, 39 Rue Camille Desmoufins, 94805 Villejuif, France," 3Cancer Therapy Department and Medicinal Biochemistry Division, Burroughs Wellcome Co., Research Triangle Park, NC 27709, USA

Key words: crisnatol, phase I, infusion, continuous

Summary Crisnatol mesylate is a rationally designed cytotoxic arylmethylamino-propanediol with broad spectrum cytotoxic activity. A phase I study with an unconventional escalation scheme was developed using a constant drug infusion rate (mg/m2/hr) and prolonging the infusion duration from 6 to 96 hours. Sixty-five patients received crisnatol at doses from 18 m g / m 2 in 6 hrs to 3400 m g / m 2 in 72 hours. The dose-limiting toxicity in two of five patients at 2700 m g / m 2 and two of three patients at 3400 m g / m 2 was neurologic and consisted of a syndrome of confusion, agitation, and disorientation. Phlebitis mandated the use of a central line. The mean terminal phase half-life (T1/2~) was 3.3 hours with a total body clearance (CL) of 22.8 L / h r / m 2 and a volume of distribution (Vdss) of 53 L / m L The median steady-state peak plasma concentration (Css) at 2700 mg/m2/72 hours was 2.7 tzg/ml and at 3400 mg/m2/72 hours was 3.8 ~g/ml. No responses were seen. The maximum tolerated dose (MTD) on this schedule is 2700 mg/m~/72 hours in patients with no liver disease and good performance status.

Introduction Crisnatol mesylate is a rationally designed, lipophilic cytotoxic arylmethylaminopropanediol with preclinical activity in leukemia and solid tumor models [1]. It is a potent DNA intercalator, but its exact mechanism of action is unknown. Evidence suggests that crisnatol may also induce DNA strand breakage and inhibit topoisomerase II [2]. Experimental tumor activity, comprising both survival prolongation and cures, has been demonstrated in P388, L1210, and IV Lewis lung models ([1]; R.L. Tuttle, personal communication). Lesser activity has been seen against B16 melanoma and M5076 rhabdomyosarcoma. Variable activity was seen against subcutaneously implanted colon 38. In human tumor xenografts, minimal activity was not-

ed in small cell lung cancers, H82 and H69, and in colon, HT-29. In P388 intercalator-resistant sublines, crisnatol had mixed activity ([4]; R.L. Tuttle, personal communication): full activity against actinomycin-D resistant sublines, partial activity in doxorubicin and mitoxantrone resistant sublines, and total cross resistance with amsacrine. In the human tumor stem cell assay, cytotoxic activity was seen for renal cell, melanoma, small cell lung, and ovarian tumors. Experimental activity was best at the highest concentration of crisnatol, 10 ~g/ml, above the plasma concentration range clinically achievable, and with continuous exposure of the cells to drug (D.D. Von Hoff, personal communication). Preclinical pharmacokinetic studies have shown that crisnatol achieved peak plasma level after 30

42 minutes with a tl/2 of 30 minutes in beagle dogs and one hour in the rat. Extensive tissue penetration, including penetration into the brain, was noted in the rat [4]. In preclinical studies, seizure activity was the acute dose-limiting toxicity following bolus intravenous dosage in the rat [5]. No hematologic or clinical chemistry changes were noted. The LDI0 in the rat was 29 mg/kg on a single bolus dose and 19 m g / k g / d a y when drug was administered in five daily doses. In dogs, acute CNS changes included ataxia, tremors, and convulsions. To avoid the acute CNS toxicity, crisnatol was subsequently administered by infusion at a rate of 1 mg/min. At doses of 12, 24 and 36 mg/kg daily for five days, no toxicity was noted. Convulsions were noted, however, in two of four dogs treated at 1 mg/min continuously for five days and in all dogs treated with infusions of 2 rag/rain and 5 mg/min (R.L. Tuttle, personal communication). The current phase I study was designed to deliver the maximum amount of drug while avoiding the acute CNS toxicity observed in the preclinical studies. To that end, an unusual protocol was employed utilizing infusion administration of a constant concentration of crisnatol and escalating the infusion duration to increase the total dose administered.

Materials and methods

Patients with non-hematologic malignancies, refractory to standard therapy, were eligible. Patients were required to have performance status ECOG 0-2 and life expectancy of at least three months. A normal CT scan of the brain was required. The patients were required to have a bilirubin ___ 2.5 mg/dl, a serum creatinine ___ 2.0 mg/dl, and a normal CBC. After documentation that a dose level was safe, patients with abnormalities of liver or renal function were allowed entry onto the study to obtain further pharmacokinetic data. Patients were excluded if CNS lesions, significant heart disease or history of seizures was present. No chemotherapy or radiotherapy could have been received in the previous three weeks (six weeks if treatment in-

cluded nitrosoureas), and patients had to have recovered from the toxicity of previous treatment. Pregnant patients and those < 16 years of age were excluded. All patients gave informed consent. The protocol and consent were reviewed and approved by the Human and Animal Investigation Committee at Wayne State University. Pretreatment evaluation included a complete history and physical examination. Baseline laboratories included complete blood count, blood chemistries, urinalysis, electrocardiogram, and EEG. Appropriate scans and radiographs for measurement of tumor masses were performed.

Drug formulation Crisnatol was provided in 10 ml and 30 ml vials containing the mesylate salt equivalent to 50 and 150 mg of free base. It was reconstituted with 30 ml of Bacteriostatic Water for Injection with benzyl alcohol, USP to produce a solution containing 5.0 mg/ml. Further dilutions were made with 5% dextrose in water.

Drug administration and escalation scheme At least three patients were entered at each dose level. Patients begun at one level were escalated to higher levels, only when the latter dose had been demonstrated to be safe in previously untreated patients. Patients were retreated at monthly intervals in the absence of progressive disease or unacceptable toxicity. Dose escalation was to continue until severe but reversible toxicity was observed in two of three patients treated at a given level. Crisnatol was administered by intravenous infusion. The duration of infusion ranged from 6 to 96 hours. The starting dose was 18 m g / m 2 over 6 hours. In general, dose increments were obtained by lengthening the infusion, while keeping constant the drug delivery rate. Ultimately, to avoid prolonged hospitalization of patients, the drug delivery rate was escalated to maximize the total drug dose deliverable within a 72-hour period.

43

Response and toxicity criteria. Patients with measurable or evaluable disease were permitted on study. The usual criteria for response were utilized [6]. Toxicity was graded employing the NCI comm o n toxicity criteria. Pharmacokinetics. Blood samples were obtained at initiation of therapy, at multiple times throughout the infusion, and up to 24 hours following the completion of therapy. Samples were centrifuged, and the plasma eluted, frozen, and subsequently analyzed. For initial study patients, urine samples were collected for the duration of the infusion. Samples were assayed by an H P L C technique described by H a r m a n et al. [7]. Pharmacokinetic analysis was performed by compartmental analysis of individual patient plasm a concentration-time data. The two-compartment open model with zero-order infusion was found to be most suitable for parameter estimation. Nonlinear regression analysis using N O N L I N [8] with a weighting of 1/y was used to estimate the volume of distribution of the central c o m p a r t m e n t (Vc) and the micro-rate constants. Values of the tl/23, VDss, and CL were subsequently calculated. The area under the plasma concentration-time curve (AUC) was calculated by the linear trapezoidal method to the last measurable data point and extrapolated to infinity.

Table 1. Dose levels - courses delivered 18 rag/m2/6 hr.-7 36 mg/m2/12 hr.-8 54 mg/m2/18 hr.-4 72 mg/m2 24 hr.-9 108 rng/m2/36 hr.-3 144 mg/m~/48 hr.-9 180 mg/m2/60 hr.-5 216 mg/m~/72 hr.-7 252 rng/m2/84 hr.-13 288 mg/m2/96 hr.-10

300 mg/m2/30 hr.-5 375 mg/m2/36 hr.-10 450 mg/m2/48 hr.-7 600 mg/m2/60 hr.-5 750 mg/rn2/72 hr.-4 900 mg/m~/72 hr.-4 1800 mg/m2/72 hr.-4 2700 mg/m~/72 hr.-9 3400 mg/m2/72 hr.-5

Dose escalation Therapy was initiated with a 6-hours infusion of 18 m g / m 2 (3 mg/m~/hr) with escalations by 6 and then 12 hours increments. After achieving a 96-hours infusion with minimal toxicity, the drug delivery rate was increased to 12.5 m g / m ~ / h r and the time sequence was restarted at 24 hours with six hour escalation increments. For logistic consideration, the duration of infusion was fixed at 72 hours and the infusion concentration then escalated to the MTD. (Table 1). One hundred and twenty eight courses of therapy were delivered. Patients received a median of two courses (range 1-5).

Toxicity Results Sixty-five patients, comprising 34 men and 31 women were entered on study. The median age was 58 (range 18-77) years. The median performance status was 1 (range E C O G 0 - 2 ) . Tumors included sarcomas, 11; carcinomas of lung, 13; colon, 14; ovary, 6; kidney, 6; as well as a variety of other neoplasms, 15. Most patients had been heavily pretreated. Twenty-eight had received chemotherapy. Thirty-four had received both chemotherapy and radiotherapy. The median number of previous chemotherapy regimens was two.

The dose-limiting toxicity was neurologic (Table 2). In its most severe form (grade 3), it consisted of a constellation of abnormalities including severe confusion a n d / o r disorientation, severe agitation, hallucinations, and in one patient, vertigo with nystagmus. In all but this last patient, no focal findings were noted. EEG changes in a patient with the most severe cortical abnormalities showed only diffuse slowing. Toxicity was noted as early as 1 2 - 2 4 hours from the start of infusion. In all patients, toxicity resolved over 3 - 1 2 hours after cessation of the infusion without residual abnormalities. The severe toxicities described above were seen in one of three patients at 216 m g / m 2, one of three at 288 m g / m 2, two of five at 2700 m g / m 2 and two of three at 3400 m g / m L Drug infusion was halted

44 Table 2. Toxicity

Type (NCI grade) Neurologic: Severe Agitation Confusion Disorientation Hallucination Somnolence Dizzy/Vertigo Gastrointestinal: Nausea/Vomiting

Renal: Renal Failure

Dose (dose range)

(3) (3) (3) (3)

mg/mV3d mg/mV3d mg/mZ/3d mg/mV3d

1 1 2 2

(1 - 2) (1 - 2)

(144/18hr - 3400 mg/mV3d) (144/18hr - 1800 mg/mV3d)

10 8

(1 - 2) (3)

( 1 8 / 6 h r - 2700 mg/m2/3d) (1800-3400 mg/mV3d)

23 3

(4)

Cardiac: Arrhythmia Hypertension Hematologic: Thrombocytopenia Phlebitis:

216 288 2700 3400

Number of patients

288 m g / m V 4 d

1

(54/18hr - 2700 mg/mV3d) 2700 m g / m V 3 d

11 1

(3)

whenever such toxicity occurred. Therapy was restarted in both patients at doses of 216 m g / m 2 and 280 m g / m 2. Among the four patients receiving the higher two levels, drug was reinitiated only in one patient whose therapy was completed with a slower infusion, 66~ of the initial rate. Predispositions to the increased toxicity are unclear. Four of the six patients had a performance status of 2 when therapy was initiated. Additionally, two patients were on concurrent morphine infusions. Three patients had significant liver involvement, though all had normal serum bilirubin at the time of the trial. Crisnatol plasma levels did not correlate well with severe toxicity (vide infra). In addition to these severe toxic events, milder neurotoxicity was seen in a number of patients and included somnolence (10 patients), and dizziness/ vertigo (8 patients). Additional toxicities were noted. Severe phlebitis was seen early in the trial. Because of the long durations of infusion and the potential for phlebitis, central venous access was mandated for all patients in later stages of the trial. Nausea and vomiting

3400 m g / m V 3 d

1 N/A

were severe in three patients and mild to moderate in an additional 23 patients. Arrhythmias documented under circumstances of routine continuous cardiac monitoring were seen in 11 patients. These consisted primarily of atrial premature beats and atrial tachycardia, which were not clinically significant, were self-limited, and did not require termination of therapy. Hypertension was seen in one patient at the time of severe agitation. Renal failure occurred in one patient who started therapy with a cisplatin-induced serum creatinine of 2.4 mg/dl. The serum creatinine rose to 3.7 m g / d l and ultimately to 7.7 mg/dl. The damage was renal tubular in origin and was not reversible. Thrombocytopenia was seen in one patient whose treatment at 3400 m g / m 2 was halted after 12 hours because of severe confusion. Shortly after treatment the patient's platelet count decreased from 107,000/mm 3 at baseline to 45,000/ram 3. No marrow examination could be obtained. Recovery occurred over the subsequent two weeks. In the two weeks prior to treatment with crisnatol, the patient had received heparin therapy for treatment of a

45 Crisnatol: Plasma concentration-time profiles

,03]

CRISNATOL PATIENT 10 (P40-02) 103=

Z~

CRISNATOL PATIENT 14 (P40-02)

Z~ Course 1 D

102-:

z~ Course 1 El Course 2 9 Course 3

102=

I

o

Z 0 0

- ....... ......

o

Z 0

10

o

0

10

20

30 TIME

40

50

(hr)

10

0

20

40

60 TIME (hr)

80

100

Fig. 1. Patient received 72 mg/m2/24 hrs. for 3 courses.

Fig. 2. Patient received 108 rag/m2/36 hr. course 1; 144 mg/m2/48 hr. course; 180 mg/rn2/60 hr. course 3.

deep vein thrombosis. With the exception of this episode of thrombocytopenia, there was no myelosuppression noted with crisnatol therapy.

108, 144, and 180 m g / m 2 over 36, 47, and 64-hr infusion durations, respectively. The three infusions were at the same rate, and, as further evidence of low intrapatient variability, the steady-state plasma concentrations achieved were all similar. In contrast to the low degree of intrapatient variability, there is substantial interpatient variability in the pharmacokinetics of crisnatol. Table 2 summarizes the pharmacokinetic parameters obtained for 27 patients with complete data. The average tl/23 was 3.5 hours (range: 1.3-9.3) and the mean CL was 22.8 L / h r / m 2 (range: 12.4-50.1). V c averaged 26.2 L / m 2 (range: 3.9-60.3) and Vdss averaged 53.0 L / m 2 (range: 22.9-87.2). There was considerable interpatient variability in CL and Vdss with coefficients of variation of 38 and 31%, respectively. There appeared to be no drug accumulation over prolonged infusions at these rates as reflected by stable steady-state concentrations of crisnatol. As such, dose and AUC are linearly related. The peak plasma concentrations varied, as expected, given the changes in infusion duration, concentration, and dose infused (Table 1). Steady-state level medians were 0.18, 0.65, 2.2, 2.7, and 3.8/~g/ml at infusion rates of 3 mg/hr, 12.5 mg/hr, 25 mg/hr, 37.5 mg/hr, and 47 mg/hr, respectively. Neurotoxicity correlated only very generally with peak plasma level: severe toxicity was seen in patients with levels of

A n t i t u m o r activity

No complete or partial responses were seen. One patient with renal cell carcinoma had stable disease for eight months. Two patients with non-small cell lung cancer had stable disease for approximately six months. P h a r m a c o k i n e t i c studies

Complete plasma pharmacokinetic studies were done on the first 32 patients, and steady-state concentration values were obtained on the subsequent 33 patients (Table 2). Urinary excretion was minimal in the first few patients. Further renal excretion studies were not done. Typical plasma concentration-time profiles for two of the patients with complete data appear in Figs. 1 and 2. A computer generated curve-fit is superimposed onto the plots. Patient 10 (Fig. 1) received 72 m g / m 2 crisnatol over 24 hours on three separate occasions. The data are almost superimposable suggesting that the intrapatient variability for this individual is quite low. Figure 2 contains data from a patient who received

46 0.10, 0.11, 1.9, 2.7, 3.9, and 10.0/~g/ml. Of 11 patients with peak plasma levels >_ 1.6 t~g/ml, 4 had severe neurotoxicity and 5 showed modest changes including mild to moderate somnolence or fatigue.

Discussion Crisnatol is the first in a family of arylmethylaminopropanediols to be clinically evaluated. Broad spectrum antitumor activity was suggested from the stem cell assay (D.D. Von Hoff, personal communication). Of the arylmethylaminopropanediols, crisnatol has the special characteristic of high lipophilicity. Preclinical evaluation suggested that crisnatol would have neurotoxic, cardiodepressant and lidocaine-like local anesthetic properties but no hematopoietic toxicity. Neurotoxicity was related to the rate of infusion and concentration of the administered crisnatol in these preclinical studies. This was one of three phase I studies evaluating the toxicity and possible efficacy of crisnatol. Crisnatol was also given by six-hour infusion at doses of 7.5-516 m g / m 2 [7]. Because of neurotoxicity in that trial, also, the infusion time was extended beyond six hours once the initial MTD had been attained. A maximum dose of 900 m g / m 2 was delivered over 18 hours, at a rate of 50 mg/mVhr. Among patients receiving the higher rate of infusion, acute encephalopathy was seen in one patient and milder symptoms in 7 of the 14 remaining patients. Nausea, vomiting, and transient hypertension were also seen. In a second trial, a two hour infusion was utilized [9]. The maximum dose was 400 m g / m 2 with the dose-limiting neurotoxicity. In neither study was any objective response seen to crisnatol therapy. The trial design of our study employed an unusual escalation scheme in recognition of this potential for neurotoxicity. The drug delivery rate of the infusion was maintained as a constant and the duration o f the infusion was progressively lengthened. Only when the infusion time became too lengthy with low steady-state plasma levels was the rate increased. This maneuver allowed a 72hours infusion MTD to be defined by the anticipated neurotoxicity.

Trials utilizing constant administration rates and progressive prolongation of infusion duration have thus far not been widely used in phase I evaluations. When preclinical studies suggest that toxicity is related either to a peak plasma level or to an AUC above a toxic threshold level, such a trial design may be much more logical and productive than current standard protocols. This trial required entry of a larger number of patients than the usual phase I study. In part, this large number was necessitated by the low starting dose mandated by the " 1 / 1 0 t h the LD10" rule and in part by a conservative escalation scheme. The latter was utilized because neurotoxicity, a toxicity which is still relatively infrequent in clinical studies, is difficult to critically describe and quantitate, and commands extra concern and caution by treating physicians. In retrospect, more relevant modeling of the conditions, dosing scheme, and pharmacokinetics at a preclinical level might have permitted a higher starting dose for an infusion and a more rapid escalation of dose [10, 11]. The MTD in this trial was 2700 m g / m V 3 days with repeated cycles every four weeks. Patients with severe liver abnormalities, poor performance status, or requiring parenteral opiates appeared to be more sensitive to crisnatol and will require dose reduction. The MTD was achieved utilizing an infusion rate of 37.5 m g / m V h r . Infusions delivered at lower rates were, in general, better tolerated without CNS toxicity. We did not examine the tolerance or toxicity of infusions lasting longer than three days at this delivery rate. Nor did we study more frequent treatment cycles. It is possible that crisnatol, which demonstrated no hematopoietic toxicity and no delayed toxicity, could be infused either for longer durations at lower concentrations, a n d / o r courses of therapy could be delivered at more frequent intervals. The toxicity profiles of such treatment alternatives remain to be determined. The neurotoxicity of crisnatol was profound. The etiology of the neurotoxicity is unknown. In in vitro conduction studies using the crayfish giant axon, crisnatol produced electrophysiologic effects similar to and 100-fold more potent than those of lidocaine H C L (R.L. Tuttle, personal communica-

47 tion; [3]). W h e t h e r such m e m b r a n e effects are responsible for the n e u r o t o x i c i t y has n o t been det e r m i n e d . F o r o p t i m a l l y safe use o f crisnatol, however, further studies of the n e u r o t o x i c i t y are required. I n a d d i t i o n , n e u r o c o r t i c a l toxicity is poorly u n d e r s t o o d a n d characterized at a clinical level. C o n c u r r e n t clinical neurological e v a l u a t i o n of patients receiving crisnatol should c o n t i n u e to better define its n a t u r e .

Acknowledgements T h e a u t h o r s wish to t h a n k D e b o r a h Bulkowski a n d Ai-ly Hsieh for their technical expertise in the analysis of p l a s m a a n d A n n Zdilla in the p r e p a r a t i o n of this m a n u s c r i p t . This m a n u s c r i p t was s u p p o r t e d in p a r t b y Burroughs W e l l c o m e Co., Research Triangle P a r k , N o r t h C a r o l i n a 27709 U S A .

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BW A7704: An antitumor DNA intercalator that displays limited and nonpleiotropic cross resistance to other antitumor agents (Abstr). Proc AACR 28:300 (#1188), 1987 4. Woolley Jr JL, Wargin WA, Hsieh A, Liao SHT, Blum MR, Crough RC, SigelCW: Disposition of the arylmethylaminopropanediol BW A77OU in the rat and dog (Abstr). Proc AACR 27:423 (#1682), 1986 5. Everitt BJM, Grebe G, Mackars A, Macklin AW, Shisnant JK, Tuttle RL: Comparative pharmacology and toxicology of three arylmethyaminopropanediols (AMAPs): BW A77OU, BW 773U, BW A502U (Abstr). Proc AACR 27:424 (#1686), 1986 6. Miller AB, Hoogstraten B, Staquet B, Winkler A: Reporting results of cancer treatment. Cancer 47:207-214, 1981 7. Harman GS, Craig JB, Kuhn JA, Luther JS, Turner JN, Weiss GR, Tweedy DA, Koeller J, Tuttle RL, Lucas VS, Wargin W, Whisnant JK, and Von Hoff DD: Phase I and clinical pharmacology trial of crisnatol using a monthly single-dose schedule. Cancer Res 48:4706-4710, 1988 8. Metzler CM, Elfring GL, and McEmen AJ: A package of computer programs for pharmacokinetic modelling. Biometrics 30:562, 1974 9. Albert DS and Dalton WS: Phase I evaluation of crisnatol on a single-dose schedule in patients with responsive clonable tumors. Phase I/II Transitions Investigators' Workshop, March 2-4, 1989 10. EORTC Pharmacokinetics and Metabolism Group: Pharmacokineticallyguided dose escalation in phase I clinicaltrials. Commentary and proposed guidelines. European J Can & Clin Oncol 23:1083-1087, 1987 11. Collins JM, Zaharko DS, Dedrick RL, and Chabner BA: Potential roles for preclinical pharmacology in phase I clinical trials. Cancer Treat Rep 70:73-80, 1986

Address for offprints: E. A. Poplin, Harper Hospital, Division of Hematology and Oncology, P.O. Box 02188, Detroit, MI 48202-0188, USA