CANCER AND
`CHEMOTHERAPY
`
`Volume III
`
`Antineoplastic Agents
`
`Edited by
`
`Stanley T. Crooke
`Rcseanch and Development
`Smith Kline & French Laboratories
`
`Philadelphia, Pennsylvania
`and
`
`Department of Pharnlacology
`Baylor College of Medicine
`Texas Medical Center
`
`Houston, Texas
`
`Archie W. Prestayko
`Research and Development
`Bristol Laboratories
`
`Syracuse, New York
`and
`
`Department of Pharmacology
`Baylor College of Medicine
`Texas Medical Center
`Houston, Texas
`
`Edtrrma! Assistant
`
`Nancy Alder
`
`1 98]
`
`ACADEMIC PRESS
`
`A SuIm'diary afIIarcow'! Brace Jovanovmh, Publ;'shcr's
`New York London Toronto Sydney San Francisco
`
`MEDAC Exhibit 2012
`
`ANTARES v. MEDAC
`
`IPR2014-01091
`
`Page 00001
`
`MEDAC Exhibit 2012
`ANTARES v. MEDAC
`IPR2014-01091
`Page 00001
`
`

`
`CUPYRIGEIT © 1981, BY ACADEMIC PRESS, INC.
`ALL RIGHTS RESERVED.
`N0 PM{'I‘ or ‘nus I’.UBLlC.v\T10N MAY BE REPRODUCED on
`'1‘RANSMI‘l"[‘F.D IN Am: FORM on 131' ANY MEANS, ELECTRONIC
`on MECI-IANICAL, INCLUDING PHCITOCOPY, RECORDING, on ANY
`INFORMATION sToI:AoB AND RETRIEVAL SYSTEM, wrrHou'-1‘
`PERMISSION IN WRITING FROM THE‘. PUBLISHER.
`
`ACADEMIC PRESS, INC.
`111 Fiflh Avenue, New York, New York 10003
`
`U.-u':‘ea' Kirrgdom Edition published by
`ACAIJEMIC PRESS, INC. (LONDON) LTD.
`24/28 Oval Road. Lands;-I1 NW1 TDX
`
`Library of‘ Congress Cataloging in Publication Data
`Main entry under title:
`
`Cancer and chemotherapy.
`
`Includes bibliographies and index.
`CONTENTS: V. 1. Introduction to neoplasia and
`antineoplastic chemotherapy——v. 2. Introduction
`to clinical oncology~—v. 3. Rntineoplastic
`agents.
`1. Cancer-—Chemctherapy. 2. Antineoplastic
`agents. 1. Crooke, Stanley T. II. Prestayko,
`Archie W.
`EDNLM: 1. Neop1asms——Drug therapy.
`2. Antineoplastic agents.
`cz257.c21a]
`RC667.C28
`6l6.99'4U6l
`79-8536
`ISBN 0—12~197803—6 (v. 3)
`
`PRINTED IN THE UNITED STJKTES OF AMEIKICA
`
`31328384
`
`937654321
`
`Page 00002
`
`Page 00002
`
`

`
`22
`
`METHOTREXATE:CLDflCAL
`
`Pd1}XI{hd}\(3()l1)(3STiAlJI)
`
`THERAPEUTIC APPLICATION
`
`J. R. Bertino
`
`.
`
`.
`.
`
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`Intmduction
`I.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`,
`II. Pharmacology
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`A. Mechanism of Action
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`B. Absorption
`.
`.
`.
`.
`.
`C.
`Plasma Disappearance and Distribution .
`.
`.
`D. Metabolism .
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`E.
`Excretion
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`F.
`Drug Interactions
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`' III. Clinical Applications .
`.
`.
`.
`.
`.
`.
`,
`.
`.
`.
`A. General Considcrations-- -Guidelines for Use .
`B.
`Indications
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`C.
`Toxicity .
`,
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`IV. Discussion .
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`References .
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`
`.
`.
`.
`
`.
`.
`.
`.
`.
`.
`.
`.
`.
`,
`.
`.
`.
`.
`
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`. _.
`.
`I
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`.
`
`.
`.
`.
`.
`.
`.
`.
`,
`.
`.
`.
`.
`l
`.
`
`.
`.
`.
`.
`.
`.
`.
`.
`.
`,
`.
`.
`,
`.
`
`359
`360
`360 '
`360
`361
`362
`363
`363
`363
`363
`366
`367
`371
`372
`
`I. INTRODUCTION
`
`Methotrexate (MTX) continues to be a valuable drug for the treatment of
`human neoplastic disease. Attempts to increase its efficacy over the years since
`its introduction into the clinic in 1948 (Father er al., 1948) have involved
`evaluation of various dosage schedules, as well as its use in combination with
`other drugs (Be1'tino, 19'Jr'9). Doses have escalated from 1-5 mg/m2 per day to
`very
`high
`doses
`(1-20 gmfmg),
`followed
`by
`leucovorin (LV, N”-
`formyltetrahydrofolate) “rescue” (Bertine, 1977). The use of MTX in these high
`doses has led to a reexamination of the clinical pharmacology of this drug in an
`attempt to prevent serious drug toxicity. This chapter will discuss the clinical
`
`CANCER AND CHEMO'l'HERz‘\l’Y, VOL. III
`Copyright © I981 by Academic Press. Inc.
`All rights of reproduction in any form reserved.
`[SH-N U-1?.-197303-6
`
`359
`
`Page 00003
`
`Page 00003
`
`

`
`360
`
`J. R. Bertino
`
`pharmacology and clinical application of MTX, with emphasis on high-dose
`regimens.*
`
`II. PHARMACOLOGY
`
`A. Mechanism of Action‘?
`
`The biochemical event that leads to cell death following MTX administration
`appears to be powerful, and in certain circumstances (pH 6.0), “stoiehiomct-
`ric," inhibition of the enzyme dihydrofolate reductase (DHFR) (Werkheiser
`1961; Bertino, 1963; Bertino er al.. 1964). Inhibition of this enzyme activity
`leads to decreased tetrahydrofolate formation, and consequent
`inhibition of
`thymidylate and purine biosynthesis (Johns and Bertino, 19'i'4; Chabner and
`Johns, 1977) (see Fig. 3, Beitino, Chapter 18, this volume). Therefore cells
`undergoing DNA synthesis during the S phase of the cell cycle are susceptible to
`MTX, and this drug acts primarily on cells undergoing rapid growth (Bruce et
`at, 1966; Hryniuk at al., 1969).
`In leukemia cells, MTX appears to be transported by an active, carrier-
`mediated transport system, utilized by the naturally occurring folates, leucovorin
`(5-formyltetrahydrofolate, LV) and 5-methyltetrahydrofolate (Nahas at al.'.,
`1972; Goldman et at'., 1968, 1971; Bender, 1975). Folic acid, which is poorly
`transported, apparently does not use this system (Nahas er al,'., 1972; Huenne-
`kens er al.. 1978). MTX, therefore, also acts to compete with reduced folates for
`transport into cells. MTX also acts to facilitate efflux of reduced folates from
`cells, thus adding to the relative folate “starvation" caused by impairment of
`- reduced folate transport. Thus MTX not only prevents reduced folate resynthcsis
`by inhibiting DHFR, but also in high concentration inhibits influx of folates and
`stimulates efflux of reduced folates (Goldman, 1971).
`
`B. Absorption
`
`Methotrexate is a relatively polar, weak dicarboxylic acid (the pK,,s of the
`glutamate carboxyl groups are 4.8 and 5.5) (Seegar er al., 1949; Liegler er ai'.,
`1969). In doses of up to 30 mglma the absorption is almost complete (Henderson
`er a!., 1965; Huffman er al., 1973). Peak blood levels are reached in 1-2 hr
`when the patient is in the fasting state. As doses exceed 30 mg/in“, proportionally
`less drug is absorbed (Henderson eraI., 1965; Wan et all, 1974), and high-dose
`regimens are administered via the intravenous route. MTX can also be adminis-
`tered S.C., I.M., or I.P.; peak blood levels are rapidly achieved in 15-30 min.
`
`*l"'or other recent reviews, see Bertino (1977), Chablier and Johns (1977), and Bleyer (1978).
`‘i’ For a more detailed description of the chemistry and rneclianism of action of this drug see chapter
`18, this volume.
`
`Page 00004
`
`Page 00004
`
`

`
`22. Melhotrcxate: Clinical Pharmacology
`
`36]
`
`The drug can also be administered intratheeally; in this circumstance the drug
`slowly leaks out of the cerebrospinal fluid (CSF) and plasma levels are main-
`tained for two to three times longer than would be expected after intravenous
`administration (Jacobs er al., 1975b). Thus there is more potential for systematic
`toxicity after intrathecal administration than after a given dose administe1'ed
`parenterally (Jacobs er al.,
`l9'r'5b; Cadman at al., 1976).
`
`C. Plasma Disappearance and Distribution
`
`After intravenous administration, plasma half-life values have been measured,
`and "a triphasic curve has been described (Huffman er al.,
`l9’i'3; Stoller er at'.,
`1975}. 'l‘he initial half-life lasts about 0.'.r'5 hr and reflects the distribution phase.
`Calculations of the volumes of distribution indicate that the drug is distributed
`
`initially in the extracellular space and then in total body water (Leme et al..
`'l9'l'5; Henderson er al., 1965). A second phase (3% = 2—3 hr) can also be
`identified, which probably reflects the renal clearance of the drug (Isacoff er al.,
`1976, 1977). A terminal phase can also be measured when plasma levels de— -
`crease below l0‘7 M (24-48 hr after high-dose therapy) (Stoller et al.,
`I975).
`This phase has a half—life of 10 hr and may be the result of enterohepatic
`circulation of the drug. Toxic effects of MTX may be the result ofthis prolonged
`third phase, since DNA synthesis in replicating tissues may be inhibited until
`plasma levels fall below 10"“ (Chabner and Young, 19733). Experiments in mice
`in which. this terminal phase is eliminated by carboxypeptidase G,, an MTX—
`degrading enzyme, have demonstrated that much of the toxicity of MTX is
`relieved (Chabner er al.,
`i972).
`Distribution of MTX into the CSF, peritoneal, and pleural cavities occurs
`slowly. In the presence of pleura] or peritoneal effusions, these “third” spaces
`may act as reservoirs and prolong plasma MTX disappearance with an increase in
`systemic toxicity (Creavan ei al., 1973; Tattersall er al., 1975). When large
`doses of MTX are used (>500 mgfm”), high CSF levels are achieved (> 10”‘ M)
`(Shapiro et ai., 1975; Tattersall er al., 1975b). Presumably, these CSF levels are
`the result of the high plasma levels (l0‘” M) and reflect a small amount of
`unchanged drug that penetrates this barrier.
`'
`Organ distribution of MTX appears to reflect
`the presence or absence of
`specific transport mechanisms, as well as the levels of DHFR present in the cells,
`and perhaps the amount of conversion to oligoglutamates (Whitehead at al.,
`l9"l'5). The organs that contain the highest levels of MTX and retain it for the
`longer periods of time are the liver and kidney (Charache et al., 1960; Anderson
`I at a!., 1970). A study utilized 131I—labeled aminopterin showed that these organs
`rapidly took up this folate analogue and retained it for long periods of time (Johns
`er al., 1968). Until recently it was believed on the basis of displacement of tissue
`folates into the urine, and characterization of the inhibitor by chromatography
`and by enzyme inhibition, that the material bound in tissues was unchanged
`
`Page 00005
`
`Page 00005
`
`

`
`362
`
`J. R. Bertino
`
`MTX (Johns at al., 1964).. More recently, it has been clearly shown that MTX is
`present in liver and tumor tissues, at least in part, as oligoglutamates (Whitehead
`at £11., 1975; Jacobs et ai., 1975a). Since plasma contains conjugase activity, any
`oligoglutamates of MTX would be hydrolyzed and the monoglutamate of MTX
`excreted. The MTX (or oligoglutamates) remaining in these tissues after the
`plasma level decreases to l()‘9 M or lower has been shown to be bound prima_rily
`or even exclusively to Di-IFR.
`In fact, Werkheiser (1961) and Bettino et at.
`(I965) have suggested that liver or blood cells, respectively, can be labeled in
`this manner, and measurement of the decay of the MTX concentration in these
`populations can be used to measure the life span of the cells.
`- Although the rat actively secretes MTX in the bile, biliary excretion is less
`prominent in humans, and about l—6% of the drug is estimated to be lost by this
`route (Creavan er a!.,
`l9?3). The amount excreted in the bile may be propor-
`tional to the dose (Bleyer, 1978).
`Approximately 50% of the plasma MTX concentration is weakly bound by
`plasma proteins, mainly albumin (Lieglcr er al.'., 1969; Wan er at., 1974). This
`binding can be competed for by drugs such as aspirin and sulfa, sulfonamides,
`and presumably reflects nonspecific binding by the p-aminobenzoy]-glutamate
`part of the molecule (Liegler et af., 1969).
`
`D. Metabolism
`
`When small or conventional doses of MTX are administered to humans, rela-
`tively littlc metabolism of the drug occurs. After most of the drug is excreted in
`the first 24 hr, a small amount of drug and a metabolite, apparently a pteroate
`derivative (Johns er al., 1964; Valerino et at‘, 1972), is excreted in the urine
`' each day for several weeks thereafter, presumably reflecting cell breakdown
`(Johns et at., 1964). During the terminal phase of the plasma MTX disappear-
`ance, some 2,4—diarnino-N‘°—methylpteroic acid can be detected in plasma and
`the urine (Johns ct (IL, 1964; Y. Wang et at., 1976). This metabolite presumably
`occurs as a result of metabolism of this drug by bowel bacteria that can hydrolyze
`the terminal glutamate from MTX (Valerino at at, 1972). Recently, Jacobs er
`al. (1976) have detected an additional metabolite of MTX in the urine and plasma
`of patients receiving high doses of MTX, namely, 7—0H tnethotrexate. Large
`amounts of this metabolite ('.r‘—30% oftotal drug excreted) were found in the urine
`during the second 12 hr after MTX administration. These investigators postulated
`that hepatic aldehyde oxidase was responsible for this conversion, and that high
`MTX levels were necessary to saturate this enzyme in order for the '}'—OH com-
`pound to be formed. Since the 7-OH compounds is a much less active inhibitor of
`DHFR, it clearly represents an inactivation of the drug. The role of this metabo-
`lite in the toxicity of MTX, especially the renal toxicity, is less clear. Jacobs et
`aL, (1976) have proposed that since this derivative is less soluble than MTX, it
`could contribute to the nephrotoxicity seen with high-dose therapy.
`
`Page 00006
`
`Page 00006
`
`

`
`22. Methotrcxate: Clinical Pharmacology
`
`363
`
`E. Excretion
`
`MTX excretion is primarily renal, and for all but the smallest doses employed,
`greater than 90% of the drug is excreted within the first 24 hr after drug adminis-
`tration (Henderson er a!., 1965; Pratt et ai., 1975; Y. Wang et (11,, 1976). Two
`recent studies have indicated that with very large doses (50—200 mg/kg), less
`than 60% of the MTX could be recovered from the urine at 72 hr (lsacoff et ai.,
`19":'8; Creaven at al., 1973). At the very low plasma concentrations, MTX may
`be reabsorbed by the kidney (Huffman er al., 1973), whereas at higher concen-
`trations MTX clearance is greater than insulin clearance, indicating that there is
`active secretion by tubules as well as filtration (Liegler er (IL, 1969). A small
`percentage of an intravenously administered dose (l—2%) is found in the stool as
`unchanged drug and metabolites; most of the MTX excreted in the bile is reab~
`sorbed. After oral administration, fecal elimination is proportional to dosage; for
`example, at 30 mglmg, 4—6% was excreted in the feces, and at a dose of 80
`mgfm” 28.6% was eliminated" by fecal excretion.
`
`F. Drug Interactions
`
`Other drugs may increase or decrease MTX toxicity or therapeutic effects. By
`displacing MTX from plasma proteins, salicylates and sulfa drugs may increase
`free MTX levels in plasma, thus making more drug available to tissues and for
`renal excretion (Liegler et at., 1969; Mandel, 1976]. Weak organic acids, such
`as probenicid and salicylate, may diminish renal tubular transport (Liegler at .91.,
`I969‘, Bourke at £11., 1975). Antibiotics may interfere with the metabolism of the
`drug by bacterial flora and may decrease reabsorption (Cohen at c(., 1976).
`Other drugs such as vincristine may increase the uptake of this drug by cells
`(Goldman and Fyfe, 1974), whereas other d1'ugs such as cephalothin and hyd~
`rocortisone may decrease its uptake (Bender er al., 1975). In the L1210, but not
`the P388 mouse, lymphoma allopurinol decreased MTX therapeutic effects,
`presumably by increasing purines available for the salvage pathway (Grindly and
`Moran, 1975). It is not clear if allopurinoi decreases MTX antitumor effects in
`patients.
`
`III. CLINICAL APPLICATIONS
`
`A. General Considerations—Guidc-lines for Use
`
`MTX remains an important drug in the treatment of several human ma-
`lignancies. MTX is available for both parenteral and oral administration. Use of
`very high doses (>1.0 gmlmz) is still considered experimental, and 0.5- and
`1.0-gm lypholyzed vials for intravenous use without preservatives are only avail—
`able for protocol studies through the NCI (Catane er al., 1978).
`
`Page 00007
`
`Page 00007
`
`

`
`364
`
`J. R. Bcrtinu
`
`Current regimens in use involve (1) conventional low dosage (p.o. or l.V.)
`without
`leucovorin rescue,
`(2) moderate—dose intermittent regimens with or
`without LV, (3) high-dose regimens with LV, (4) intrathecal therapy (Table I).
`The high-dose regimens are administered as ab_olus or over 4-6 hr, or by infusion
`over 20-42 hr (Bertino, 197’7; Bleyer, 1978).
`In poorly perfused tumors or
`tumors that transport MTX poorly,
`the bolus approach may result in greater
`tumor uptake since high extracellular levels are maintained for a few hours; the
`infusion approach gives a desired blood level that is maintained for the duration
`of the infusion. Data are not available to choose between these modes of ad minis-
`
`tration; if sufficient MTX is given by bolus to result in a desired 24 or 36 hr blood
`level, then the advantages of infusion therapy would seem to be minimal. An
`additional benefit of high-dose regimens is penetration into body cavities, such as
`the CSF, giving rise to cytoeidal concentrations (> . 10”’ M) (Shipano et al., 1975;
`Abelson er al., 19791 Guidelines for the use of MTX, based on the experience
`of this center, as well as others,
`is given in Tables II and III. Experimental
`evidence would favor the use ofa high MTX dose, e.g., 1-3 g/mg as a bolus or
`18-hr infusion, to achieve plasma levels of 10*‘ M or greater for 24 hr, then the
`use of minimal leucovorin rescue (Jacobs and Santicky, 1978). Extremely high
`doses of MTX (b3.0 gfmz) may not provide much added benefit, although this
`point has not been established. Excess LV rescue could protect neoplastic cells
`from subsequent doses of MTX (Sirotnak at al., 1928; Capizzi at al.'., 1970;
`Hryniuk and Bertino, 1969).
`'
`
`MTX effects can also be ‘‘rescued'' by asparaginasc (Capizzi, 1975),
`thyrnidine (Tattersall er al., 19?5a; Howell er al., 1977), or carboxypeptidase
`(Chabner at a!.. 1972; Abelson at .01., 1979). The latter two methods are still in
`the early stages of clinical experimentation, but have some promise. The MT)(-
`asparaginasc combination appears to be synergistic in the treatment of human
`
`TABLE I
`
`Dose Schedules of MTX
`
`
`Dose
`
`Route
`
`Frequency
`
`LV
`
`1. Conventional dose
`a.
`15-20 mg;"m""
`b.
`30—5Umgi"1'n‘
`c.
`15 ingtm’ X 5 days
`II. Moderate dose
`
`l.\«". or p.o.
`l.V. or p.o.
`I.V. or I.M.
`
`50-150 mgfm“
`a.
`240 rngfm’
`b.
`0.5-1.0 gmlm’
`e.
`III. High dose
`a.
`1-7.5 gmlmi‘
`
`l.V. push
`I.V. infusion (24 hr)
`l.V. infusion (36-42 hr)
`
`l.V. (1-6 hr)
`
`2 X week
`Weekly
`q 2-3 weeks
`
`q 2-3 weeks
`q 4-? days
`q 2-3 weeks
`
`q l--3 weeks
`
`—
`—
`—
`
`—
`+
`+
`
`+
`
`Page 00008
`
`Page 00008
`
`

`
`22. Metlmtrexate: Clinical Pltarmacology
`
`365
`
`TABLE 1]
`
`Guidelines for liigh-Dose MTX ’I‘he1'apy with LV Rescue
`
`l. A normal erealinine clearance should be required before therapy. A normal serum crea-
`tinine should be required before each additional course of therapy.
`2. Alkalinize the urine before and during the M'l‘X therapy with 13.0. sodium bicarbonate
`{pH 7.0 or higher).
`U-i
`Push fluids to 3000 mll'm"‘ day during M'l‘X administration and 24 hr following.
`4. Obtain a serum creatinine and plasma or serum MTX 24 hr after starting MTX,
`a.
`if serum creatinlne is more than 50% above pretreatment levels, increase LV to
`100 mg q 6 hr and continue until plasma MTX is less than 10-” M.
`In. Adjust LV rescue according to plasma MTX (Table III].
`
`acute lymphatic leukemia as well as for experimental leukemia (Capizzi, 1975).
`Since asparaginase partly protects patients from MTX toxicity when adminis-
`tered 24 hr later,
`this technique has allowed relatively large doses of MTX
`(600--800 mgfmz) to be administered safely at q 9-10 day intervals.
`After an intrathecal injection, most patients clear M'I‘X from their CSF within
`7 days of injection, and neurotoxicity is rare if drug administration is at Tr‘ or more
`day intervals (Bleyer, 1978). If MTX is given more frequently, -monitoring of
`spinal fluid levels with appropriate dose modification can reduce the frequency of
`neurotoxieity (Bleyer er al., 1973a). Guidelines for CSF levels of MTX in
`patients treated with intrathecal MTX are given in Fig.
`1 and may be used to
`estimate subsequent dose modifications [Bleyer,
`l97r'7). Bleyer (1978) has also
`pointed out that the 12 mg/m2 conventional dose (maximum 15 mg total dose)
`was not adequate to prevent meningeal leukemia in children less than 3 years of
`age and that body surface measurements do not correlate well with CSF levels of
`MTX obtained after the 12 mgfmz dose. Table IV indicates the dosage schedule
`he suggests for intratheeal MTX; note that all patients over the age of 3 receive
`12 mg (total) of MTX, irrespective of body surface area.
`
`TABLE [II
`
`Leueovorin Rescue Schedules Folinwing High-Dose MTX"
`
`Plasma level at
`24-30 hrs"
`
`I.V dose
`
`Duration
`
`48 hr
`10-15 mgfmiiqfih
`<|.5 X l0‘fiM
`Until plasma level <5 X 10"“ M
`30 mgfing q 6 h
`1.5-5.0 X IO‘‘‘' M
`Until plasma level <5 X 10''“ M
`60-100 mgfmi q 6 h
`>5.0 X l0""’ M
` __:4__
`
`“ Modified from Jacobs and Santieky (1978).
`” After l.V. bolus or ]3—hr infusion therapy (25 grnimgj.
`
`t-.31;-
`
`Page 00009
`
`Page 00009
`
`

`
`366
`
`.l . R. Berlinu
`
`
`
`
`
`LumbarCSFnreffiofmrafecaxrcenrmrimfmorarj
`
`Fig. 1. Spinal fluid levels afler inlrathecal MTX administration. Dosage should be adjusted to
`bring the lumbar CSF MTX concentration between :1 standard deviation (SD). (After Bleyer,
`l9"r'7.)
`
`-_
`
`B. Indications
`
`During the past decade the use of high doses of MTX with LV has been
`evaluated in a variety of human neoplasms. Unfortunately, few comparative
`trials have been reported comparing results of “conventional" doses of MTX
`with high-dose leucovorin regimens. The advantages of conver1tional—dose reg-
`irncns (see Table I) are relatively low cost and ease of administration. The
`advantages of high-dose MTX with LV rescue are relatively low toxicity (with
`
`TABLE IV
`
`Guitielines for Inlrathecal Therapy
`
`
`
` Age (yr) Total MTX dose (mg)
`
`< l
`I
`2
`.333
`
`6
`8
`10
`1?.
`
`Page 00010
`
`Page 00010
`
`

`
`22. Methotrexnte: Clinical Pharmacology
`
`367
`
`TABLE V
`
`Clinical Uses of Methotrexate
`
`A. Diseases in which MTX has established effectiveness
`
`Acute lymphocytic leukemia
`Choriocarcinorna
`Breast cancer
`Oat cell carcinoma
`Osteogenic sarcoma
`Head" and neck cancer
`
`. Mycosis fungoides
`B. Diseases in which MTX has limited effectiveness
`Acute myelocytic leukelnia
`Burkitt‘s lymphoma
`Diffuse lymphoma
`Non—oat cell lung cancer
`Soft tissue sarcoma
`Gastrointestinal cancer
`Melanoma
`Ovarian and cervical cancer
`
`
`
`?°.“*'9‘E"'.*‘§-"’5‘3i‘"-3.-'-"E-"':’“}*’}‘-’I"
`
`appropriate monitoring), high levels of drug in the CSF, and, iii some circum-
`stances, improved antitumor effects. High-dose regimens with LV can also be
`incorporated into combination programs with relative safety. MTX plays an
`essential role in the treatment of several human malignancies (Table V,A). In
`other tumors MTX does not have major activity as a single agent, but its role in
`combinations is still under investigation (Table V,B).
`o
`
`C. Toxicity
`
`I. General Considerations
`
`From the previous sections it should be clear that toxicity to normal tissues
`occurs when cytocidal blood levels are maintained for sufficiently long periods of _
`time. Thus both the plasma concentration of MTX achieved as well as the
`duration of the respective level are important in predicting toxicity; however, as
`with other antirnetabolites, the toxicity is some tog function of the extracellular
`concentration times the duration that this concentration is maintained (Stollcr et
`al.,
`I975). Thus very large doses of MTX of short duration are well tolerated
`(Goldie at al., 1972). Moderate doses, if prolonged, may be lethal (Liegler at
`at., 1969; Chabner and Young, 1973). For example, if plasma concentrations of
`l0‘“ M or higher are maintained for greater than 48 hr, irreversible toxicity may
`occur, presumably because of recruitment of normal marrow and gastrointestinal
`stem cells into “cycle,” thus making them vulnerable to MTX, as S-phase
`
`Page 00011
`
`Page 00011
`
`

`
`l
`
`,
`5
`
`368
`
`_
`
`J. R. Bertinu
`
`inhibitor. If toxicity is noted, then “rescue“ with LV should be maintained until
`blood levels of MTX decrease to below l0‘3 M . a level at which DNA synthesis
`in normal marrow and intestinal mucosa cells resumes (Chabner and Young,
`1973). Furthermore, since the relationship between LV and MTX, as regards
`toxicity, is a competitive one, the higher the blood level of MTX, the higher the
`LV dose needed for “rescue" (Jacobs and Santieky, 1978; Pinedo er .91., I977).
`This Close of LV of necessity has been largely empirical, since a practical tech-
`nique for measuring blood levels of this folate, or its conversion product
`5-methyltetrahydrofolate has only just become available (Mehta at ai.,
`I978).
`These therapeutic recommendations are summarized in Tables II and Ill.
`
`2. Marrow Toxicity
`
`The limiting toxicities of MTX involve themarrow and the gastrointestinal
`tract {Hansen et a.-'.. 1971). As alluded to earlier, MTX is tolerated well in most
`dose schedules employed since the stem cell compartment is relatively unaffected
`by this S-phase inhibitor. As the differentiating compartment is decimated by
`MTX, however, the stem cell compartment becomes committed, and as a result
`more vulnerable, if MTX extracellular concentrations are prolonged. It follows
`that a given dose of MTX would be more toxic in circumstances in which the
`stem cell compartment of the marrow is already “tumed on, ” i.e., by previous X
`ray, drug administration, infection, or tumor invasion (Bruce et ai.. 1966). It
`follows also that repeated MTX administration in circumstances where the gas-
`trointestinal mucosa and marrow have not completely recovered from the previ-
`ous administration would be more hazardous. Marrow toxicity may be conven-
`iently measured by the decrease in the granulocyte count, expressed on a
`logarithmic scale (Bertino and Hryniuk, 1978). Since granulocyte levels reflect
`events occurring in the marrow 5-7 days earlier, assays of CFU’s in marrow
`would be of greater value, but from the practical sense, the granulocyte count
`suffices (Bertino and Hryniuk, 1978). Usually a greater than 1.0 log fall of
`granulocytes to levels below 500 per mm3 carries with it the potential of infec-
`tion. After a single large dose of MTX (1 -5 mglkg), the nadir is reached in about
`10 days, and in 3 weeks from the dose, recovery of the marrow function to
`normal usually has occurred (Condit ei mi, 1962; Hansen et ai., l9'.r'l). Anemia
`and thrombocytopoenia may also occur after MTX administration, either alone or
`together with leukopoenia, but these toxicities are usually less in magnitude than
`the granuloeytopoenia (Hansen et t'ii., 1971) and can be more easily handled by
`appropriate replacement therapy.
`
`3. Gastrointestinal Toxicity
`
`Gastrointestinal toxicity is usually manifested first by oral mucosa] lesions,
`which range from minimal erythema of the buccal mucosa and lower lip to severe
`ulceration of the oral mucosa and may involve the nasal epithelium (Capizzi er
`
`Page 00012
`
`Page 00012
`
`

`
`22. Methotrexate: Clinical Pharmacology
`
`369
`
`al., 1970). Mucositis may be observed 2-? days after MTX adminstration and is
`usually a function of both the drug dose and the duration of the drug administra-
`tion. It is usually necessary to stop therapy when mucositis occurs and allow for
`complete healing before the next dose of MTX is administered. Nausea and
`anorexia, and less commonly, vomiting, may be noted during or after MTX
`administration, usually with large doses. Diarrhea is also occasionally seen. With
`toxic doses of MTX, more severe gastrointestinal ulceration and bleeding may be
`produced.
`
`4. Skin Toxicity
`
`Skin toxicity to MTX occurs in 10-15% of patients and characteristically
`involves the neck and upper trunk. It can be pruritic and relatively insignificant
`and unrelated to other signs of systemic MTX toxicity; in other instances it can be
`related in general to severe MTX toxicity and can progress to severe bullous
`formation and desquamation "(Condit at at'., 1962; Jaffe and Traggis, 1975;
`Lanzkowsky et ai., 1976).
`
`5. Hair Loss
`
`Hair loss after MTX administration is uncommon, occurring prima1'ily in older
`individuals.
`
`6. Renal Toxicity
`
`Renal toxicity is relatively uncommon with conventional doses of MTX, al-
`though Condit has described several patients who developed renal failure on
`conventional doses of this drug (Condit er cn'., 1969). When this occurs and is not
`recognized in time,
`the results are usually disastrous, since the renal failure
`results in impaired excretion of the ClJ'U g and consequently prolonged high plasma
`concentrations. With large doses of the drug renal failure was a major problem
`leading to several reported deaths (Penta, 1975); if patients are screened carefully
`using creatinine clearance measurements and are alkalinized and hydrated, this
`complication may be largely obviated (Pitman er a!., 1975; Pitman and Frei,
`1976; Isacoff ct £31., 1977). It would appear therefore that renal toxicity secon-
`dary to MTX may be due to either a direct tubular effect, sometimes not a
`consequence of dose, or, more commonly, secondary to high-dose therapy and
`precipitation of the drug in the tubules. In both circumstances the renal effects are
`usually reversible, but unless appropriate action "is taken to improve elimination
`of the drug and to antidote the effects of high concentrations of MTX that result,
`patients will succumb to the consequences of hematologic and gastrointestinal
`toxicity. A major problem exists when patients develop renal failure after high—
`dose MTX. Dialysis, either alone or with charcoal, has not been useful because
`of the large tissue stores, which then replenish the plasma when dialysis stops
`(Djerassi el al., 1977); in addition MTX does not dialyze well. (Howell er a{.,
`
`Page 00013
`
`Page 00013
`
`

`
`370
`
`.] . R. Bcrtino
`
`l9".r'8). Carhoxypeptidase G, has been used with success in lowering MTX levels
`(Bertino er al., 1974; Howell et a1.. 1978), but the product of this enzymic
`inactivation of MTX is 2,4—diamino-N‘"-methylpteroic acid, even less soluble
`than MTX in urine. In some circumstances weeks of LV therapy are necessary
`with close monitoring of blood levels (Bertino, 197?).
`
`7. Hepatic Toxicity
`
`Acute hepatic toxicity is usually not a problem with either conventional or
`high—dose regimens. When liver function is monitored carefully, transient eleva-
`tion in SGOT levels is noted, but these usually return to normal. However,
`‘patients with impaired liver function should be treated with lower doses of MTX
`or not at all; enhanced toxicity of this drug may be observed in these circum-
`stances, despite thc fact that this drug is excreted primarily unchanged by the
`kidney and the liver presumably plays only a minor role in drug inactivation.
`Hepatic fibrosis and cirrhosis have been reported following chronic administra-
`tion of MTX (Wcinstein er al.,
`l9'i"3). Predisposing factors in patients develop-
`ing this complication have been frequent daily low-dose administration (greater
`than 12 daysfmonth) (Podurgiel at al., 1973) and i11 psoriatic patients, associated
`alcoholism (Roenigk er al., 1971). Intermittent therapy with high doses (80
`mg!1112 every 2 weeks) did not produce histologic evidence of liver disease, even
`after 111% to 2% years of treatment (Mclntosh er al., 1977), nor did weekly
`treatment using 3-10 mg/m2 per week (Mackenzie,
`l9'r'5).
`
`8.
`
`’I'cmtogem'c. and Mutagenic Effects
`
`MTX is known to be a potent abortifacient, especially if administered during
`the first trimester of pregnancy (Thiersch, 1962). Thus far there is no evidence
`that MTX has mutagenic or carcinogenic activity in man (Bailin ex .21., 1975).
`Women successfully treated with MTX for choriocarcinoma have not had a high
`evidence of fetal abnormalities following cessation of therapy nor have they had
`a higher incidence of secondary malignancies.
`
`9. Neurotoxicity
`
`Neurotoxicity due to MTX can occur both after intrathecal MTX and with
`systemic administration of large doses (>80 mgfmi).
`An acute syndrome has been described following intrathecal administration.
`This consists of headache, fever, mcningismus, and a pleocytosis that may
`mimic bacterial infection. This syndrome is the most common of the neurologic
`syndromes associated with intrathecal MTX and appears to be related to high
`CSF concentration of MTX (Mott er al., 1972; Bleyer at of,
`l9'i'3b).
`A subacute form of CNS toxicity has also been described following intrathecal
`use; in this circumstance more severe signs of motor dysfunction of the brain are
`noted: paraplegia, cerebellar dysfunction, cranial nerve palsics and seizures,
`
`Page 00014
`
`Page 00014
`
`

`
`22. Methotrexate: Clinical Pharmacology
`
`371
`
`usually following two or more doses of drug per week (Gagliano and Costanzi,
`1976; Weiss er al., 1974). This complication has been correlated with persis-
`tently elevated levels of MTX in the CSF (Bleyer, 1977).
`In addition to the neurotoxicity reported above after intrathecal MTX, patients
`receiving hi gh-dose MTX (>50 mg/In”) parenterally after radiation therapy to the
`brain (>200!) R) have developed a neerotizing leukoencephalopathy associated
`with progressive neurologic deterio1'ation (Bresnan er al., 1972; Hendin er a!.,
`I974; Kay er al.,
`l972;Nor1'ell er ai., 1974; Rubenstein er a.-7., 1975; Price and
`Jamieson, 1975; Shapiro er al.. 1973; Smith, 1975; Aur er al., 1976). This may
`be