Eur J Clin Pharmacol (1993) 44: 579-582
`
`EuropeanJournalof Giimicall
`hanmacology
`© Springer-Verlag 1993
`
`On the bioavailability of 2-chloro-2’-deoxyadenosine (CdA)
`
`Theinfluence of food and omeprazole
`
`E. Albertioni!, G. Juliusson2, and J. Liliemark!?
`
`' Departmentof Clinical Pharmacology, Karolinska Hospital, Stockhoim, Sweden
`? Division of Clinical Hematologyand Oncology, Department of Medicine, Karolinska Institute at Huddinge Hospital, Huddinge, Sweden
`
`Reccived: September18, 1992/Acceptcd in revised form: January 29, 1993
`
`oral CdA
`of
`pharmacokinetics
`Summary. The
`(0.24 mg/kg) was studied in 4 patients (1 with hairy cell
`leukaemia and 3 with B-cell chronic lymphocytic leu-
`kaemia) to determine any effect of food and fasting with
`and without omeprazole.
`Food intake did not significantly influence the bio-
`availability of CdA (42 % after food intake vs 46% while
`fasting) but it did reduce the maximum plasma concentra-
`tion (Cra) by 40 % ; 83 compared to 116 nM while fasting.
`The time to reach maximum concentration (tax) was
`delayed about 0.8 h after food intake. Pretreatment with
`omeprazole did not significantly influence the bioavail-
`ability of CdA (51% vs 46% without), or the interindi-
`vidual variability in bioavailability in the fasting state
`(C. V.0.26 with and C. V. 0.27 without).
`In conclusion,there was a small, though notstatistically
`significant reduction in the bioavailability of CdA after
`food intake. Omeprazole did not significantly improve the
`bioavailability of CdA.
`
`Key words: 2-Chloro-2’-deoxyadenosine (CdA); omepra-
`zole, food, pharmacokinetics, bioavailability
`
`The antimetabolite 2-chloro-2’-deoxyadenosine(CdA)is
`a purine analogue whichis resistant to adenosine deami-
`nase, probably dueto protonisation at the N-7 position [1].
`It leads to accumulation of DNAstrand breaks, thus acti-
`vating poly(ADP)ribosylation, depletion of NAD, and
`apoptosis, causing cell death both in resting and dividing
`cells [2, 3].
`CdAis the drug of choice for the treatmentof hairy cell
`leukaemia (HCL)andit is a promising drug in the treat-
`ment of lymphoproliferative disorders, such as chronic
`lymphocytic leukaemia, non-Hodgkin’s lymphomas [4~7]
`and relapsed acute myeloid leukaemia [8]. Patients with
`low-grade malignant
`lymphoproliferative diseases are
`generally treated as out-paticnts, and more convenient
`modes of administration of CdA than the i.v. route now
`used are needed.
`Wehaverecently delineated the pharmacokinetics of
`CdA in manafter oral, subcutaneous and, intravenous ad-
`
`ministration [9, 10]. Those studies suggested that subcuta-
`neous administration would be bioequivalentto 1. v. infu-
`sion. The oral bioavailability of CdA was approximately
`50%, but an AUC similar to that of an 1.v. infusion could
`be achieved by increasing the dose by 100%. Due to the
`possibility that the acid environmentof the stomach might
`cause degradation of CdA [11], omeprazole was co-ad-
`ministered when CdA wasgiven orally to fasting patients.
`The present study was undertaken to determine
`whether food intake altered the bioavailability or the
`pharmacokinetics of CdA. We also wanted to discover
`whether omeprazole, a gastric antisecretory drug which
`inhibits acid secretion by inhibition of H*, K*-ATPase,
`could improve the bioavailability of oral CdA.
`
`Materials and patients
`
`Drug synthesis
`
`CdA used in this study was synthesised by Dr. Z. Kazimierczuk
`(Foundation for the Developmentof Diagnostic and Therapy, War-
`saw, Poland [12]). The molar extinction coefficient of CdA was
`15000. A solution (2 mg-ml-') of CdA in saline (9 mg-ml~!) was
`prepared in the Huddinge hospital pharmacy and was shownto be
`sterile and pyrogen-free accordingto the standards of the European
`pharmacopoeia.
`
`Patients and treatment
`
`Four male patients, one with HCL and three with B-cell chronic lym-
`phocytic Icukaemia, participated in the studyafter giving prior in-
`formed consent (Table 1), The study was approved bythe local Ethics
`Committee at Huddinge Hospital and by the Swedish Medical Pro-
`ducts Agency. CdA was administered onfive consecutive days. The
`s.c.andi.v. (2 hinfusion) dose on Days 1 and2was0.12 mg-kg~1. The
`oral dose was 0.24 mg-kg~' administercd in saline after a standard
`breakfast or after overnight fast. Any residual CdA was rinsed from
`the dosage cup with 10 ml phosphate buffered saline (pH = 7.4) and
`was swallowed. The standard breakfast consisted of aproximately
`100 gbread,20 gham,20 gcheeseand 150 ml coffec.On Day3the pa-
`tient fasted overnight, and omeprazole 20 mg (Loscc®) was given
`orally 6 hand 1 hbefore thelast oral dose of CdA toprotect CdA from
`
`Hopewell EX1064
`Hopewell v. Merck
`IPR2023-00481
`
`Hopewell EX1064
`Hopewell v. Merck
`IPR2023-00481
`
`1
`
`

`

`580
`
`Table 1. Characteristics of the patients
`
`Patient
`Sex
`Age
`Weight
`Height
`Diagnosis
`Orderof dose
`
`year
`kg
`cm
`55
`87
`180
`1
`44
`69
`177
`2
`70
`88
`172
`3
`60
`83
`171
`4
`57
`82
`175
`Mean
`
`
`10.8 8.8SD 4.2
`
`
`CLL
`HCL
`CLL
`CLL
`
`—-,4+-,++,IV
`+-,--,+4,8C
`
`—--,+-,++4+,SC
`-~-,+-,4+4,S8C
`
`
`
`
`Male
`Male
`Male
`Male
`
`Not fasting, no omeprazole (— —); fasting, no omeprazole (+ —); fasting, omeprazole (+ +)
`
`Table 2. Summary of pharmacokinetic parameters of 2-chloro-2’-deoxyadenosine (CdA) during fasting, non-fasting and concomitant admin-
`istration of omeprazole
`
`Patient Parental—tmex (h) Cmax (anmol-1~*) AUC (nmol-h-17!) tipB(h) cL Bioavailability (%)
`
`
`
`
`route
`(l-ho!
`
`-m”*)
`~-
`+>
`00+
`-~- +-
`+
`SCIV -- +-
`+
`SCIV -- +-
`+
`-- +-
`+
`
`iv.
`0.80
`058
`053
`176
`134
`249
`977
`925
`743
`1044
`165
`216
`179
`128
`344
`47
`38
`53
`1
`s.c.
`159
`050
`058
`64
`133
`il
`660
`614
`599
`680
`153
`164
`137
`14.7
`376
`47
`45
`50
`2
`3
`8.c.
`155
`053
`O77
`38
`59
`113
`701
`397
`501
`666
`145
`126
`133
`117
`354
`28
`36
`48
`4
`8.C.
`105
`060
`046
`55
`139
`182
`454
`400
`570
`494
`74
`187
`101
`S1
`491
`44
`63
`54
`
`Mean
`125
`055
`059
`83
`116
`164
`698
`584
`603
`721
`134
`173
`138
`(111
`391
`42
`46
`51
`S.D.
`0.39
`005
`013
`63
`38
`66
`215
`249
`«102
`«2310
`4.10
`3.80
`3.20
`417
`679
`911
`12.29 2.75
`CV.
`0.31
`0.08
`023
`076
`033
`040
`031
`043
`O17
`032
`O31
`022
`023
`038
`O17
`022
`027
`0.05
`P
`NS NS NS< 0.05 NS
`
`
`
`
`
`Not fasting, no omeprazole ( — — ); fasting, no omeprazole (+ —); fasting, omeprazole (+ +)
`
`200
`
`100
`
`50
`
`bi
`
`x.
`
`OFasting, omeprazole (51%)
`© Not fasting, no omeprazole (42%)
`9 Fasting, no omeprazole (46%)
`
`from Dr. Gertrude Elion (Wellcome Foundation, Research Triangle
`Park, N.C.), was used as the internal standard and was added before
`extraction with ethyl acetate in silanized glass tubes. A C18, 3 uM
`column wasused, with a mobile phase consisting of phosphate buff-
`er, methanol, and acetonitrile (85:10:5, pH =3.0) as the mobile
`phase at a flow rate of 1 mi-min~'. The drug concentration was
`determined by UV-absorption. The inter-day variability was 8% at
`5 nmol and 5%at 100 nmol. Thelimit of sensitivity was 1 nM.
`
`Pharmacokinetic calculation
`
`PlasmaCdA,nM
`
`2 0
`
`2
`
`4
`
`6
`
`8
`
`10 12 14 16 18 20 22 24
`
`Plasma CdA concentration-time profiles were analysed by extended
`non-linear least-squares regression, using a commercially available
`program (Siphar, Société Simed, Creteil, France). The rate constant,
`Time, h
`the area under the plasma concentration versus time curve (AUC)
`Fig. 1. The mean plasma concentration of CdA in 4 patients oral ad-
`and clearance were determined. The residual area from Day 1 was
`
`
`ministration of 0.24 mg/kg CdAin three conditions. No fasting (@),
`
`subtracted from the AUC of Day 2 etc. The AUC wasalso calcu-
`
`
`fasting (0), fasting with concomitant omeprazole ([])
`lated using the trapezoidal rule and extrapolation to infinity using
`log-linear regression analysis of at least four points of the elimina-
`tion phase. The results were in agreementwith the model-dependent
`calculation. Clearance was calculated as dose/AUC, The bioavail-
`ability (f) of CdA in each patient wascalculatedas:
`
`hydrolysis in the acidic environment. The patient was prohibited from
`drinking waterfor3 handeating for 5 hafter CdA administration.On
`Days 4and5, CdA wasgiven s.c. Ori. v.
`After drug administration, blood samples were collected from a
`separate peripheral vein into heparinised tubes immediately before
`drug administration and 15, 30, 45 min and 1, 1.5, 2,2.5, 3, 3.5, 4, 6,9,
`18 and, 24 h afterwards. When administereds.c. ori.v., samples were
`also taken 5 and 10 min after administration. The samples were im-
`mediately put on ice, plasma collected by centrifugation (7 min,
`550 x G,4°C) and stored at — 20°C until analysis.
`
`F= AUC p.o. x Dose s.¢. or Lv.
`~ AUC s.c. ori.v. x Dosep.o.
`
`The observed maximum plasmaconcentration (C,,,,) and the time
`whenit occurred (tnax) were tabulated for each patient and treatment.
`
`Statistical analysis
`
`Plasma concentration assay
`
`The plasma concentration of CdA was determined using a pre-
`viously described reversed phase HPLC method[14]. Guaneran (6-
`[(-Methyl 4-nitro-5-imidazolyl)-2-aminopurine], a generous gift
`
`Statistical analysis was carried out by comparison of the pharmaco-
`kinetic parameters between the fasting and non-fasting states, with
`and without omeprazole, using one way analysis of variance proce-
`dure by ANOVA(one way analysis of variance). P < 0.05 was con-
`sideredstatistically significant.
`
`2
`
`

`

`3581
`
`A final possible mechanism is the instability of CdA
`during passage through the acid environmentof the stom-
`ach. However, there seems to be no major difference be-
`tween fasting with and without concomitant administra-
`tion of omeprazole. This suggests that acid hydrolysis in
`
`
`
`
`
`0
`
`4
`
`8
`
`12
`
`16
`
`20
`
`24
`
`Time, h
`
`Time, h
`
`=q
`<3
`
`0c
`
`a &a &q
`
`i
`
`a
`
`=q
`<as
`Oo
`ot
`&n
`&a
`
`b
`
`=¢
`<3
`QO
`
`6 &w =B
`
`q
`
`Time, h
`c
`Individual plasma concentration-time profiles CdA in
`Fig.2a—c.
`4patients after administration of a
`single dose CdA oral
`(0.24 mg/kg). a Not fasting; b Fasting; ¢ Fasting with concomitant
`omeprazole. Patient 1 (@), patient 2 (@), patient 3 (©) and, pa-
`tient 4(+)
`
`Results
`
`The bioavailability of oral CdA and the calculated phar-
`macokinetic parameters are presented in Table 2. The dis-
`position of CdA could best be described by a two-com-
`partment model[8, 9, 10]. The pharmacokinetic profile of
`CdA administered orally during the non-fasting, fasting
`and fasting state in combination with omeprazole are de-
`picted in Fig.1. The individual plasma concentration-time
`profiles of CdA are shownin Figs.2a, 2b, 2c.
`The administration of omeprazole 1 and 6h before
`swallowing the dose did not havea significant influence on
`the bioavailability of CdA (51 and 46% with and without
`omeprazole respectively). In a previous study [10] ome-
`prazole was given to all patients who were treated with
`oral CdA fasting. Addition of data from that study to the
`present, showedthat there was no difference in the inter-
`individual variation in the bioavailability between the
`fasting state with and without concomitant omeprazole,
`and after food intake (C. V. 0.26 vs 0.27 vs 0.22). Concur-
`rent food intake did show someinfluence on the rate of
`absorbtion, increasingthetmax (1.25 vs 0.55 and 0.59 h) and
`lowering the Cmax (83 vs 116 and 164 nM). The bioavail-
`ability was also slightly but no significantly lower(42 vs 46
`and 51% ) in this small cohortof patients.
`It is noteworthy that the interindividual variability in
`tnaxs Cnax and AUC wasless in the fasting state than after
`food intake (Table 2). The pharmacokinetic parameters,
`plasma clearance, volumeofdistribution and disposition
`constant were in agreement with previously reported
`values[9, 10].
`
`Discussion
`
`CdAis one of the most promising new drugsfor the treat-
`ment of low-grade malignant lymphoproliferative dis-
`eases. Oral administration would simplify the treatment
`both for patients and physicians. We have recently shown
`that the bioavailability of CdA was about 50% when ad-
`ministered to fasting patients and with omeprazole. The
`present study has provided further data on the bioavail-
`ability of CdA after food intake andafter fasting with and
`without omeprazole. Since the bioavailability of omepra-
`zole after a single doseis very low, patients were given two
`doses 6 and 1 h before CdA intake to ensure thatacid se-
`cretion was inhibited [15].
`There are several plausible explanations why the
`bioavailability of CdA was only 50%. First, its low pKa
`(1.4) [1] implies that most of the drug will be ionized in the
`alkaline environmentof the gut, which will tend to result
`in incomplete absorption. Second, there might be some
`first-pass loss in gut wali/liver. The bioavailability of CdA
`was slightly, but not significantly higher during fasting
`compared to after food intake. In the fasting condition,
`CdA is absorbed faster, which might result in more drug
`escaping first-pass loss due to the saturation of liver/gut
`wall enzymes causedbythe high portal concentration dur-
`ing the absorption phase. Bioavailability mightalso be de-
`creased by cleavage by the nucleotidases ofintestinal bac-
`teria [11].
`
`3
`
`

`

`582
`
`the stomach does not have a major effect on the bioavail-
`ability of CdA.
`The order in which patients were given CdAafterfast-
`ing or after food intake was altered, but omeprazole was
`given only on Day3 due to concern that omeprazole
`might influence drug uptake on subsequentdays if it had
`been given earlier. As described in Materials and Meth-
`ods, the residual area was subtracted from the AUC of
`subsequent days, thus minimising the risk of a systematic
`error in estimation of bioavailability after the three modes
`of oral administration.
`In conctusion, food slightly but not significantly re-
`duced the bioavailability of CdA. In the fasting condition,
`due to quickergastric emptying, a shorter t,, and a higher
`Cmax Were seen. Interindividualvariation in bioavailability
`was equalafter all three modes of administration.It is rec-
`ommended that CdA is administered orally after an over-
`nightfast.
`
`Acknoweledgements. This work wasfinancially supported by grants
`from the Swedish Cancer Foundation, the Swedish Medical Re-
`search Council, and the Jenny Foundation. We are greatful to Ms
`P.Elmlund and B. Pettersson for skilful technical assistance and to
`Dr. A.S.Rhedin forlinguistic revision.
`
`References
`
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`Proc Nat Acad Sci USA 89: 2970-2974
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`thesis of 2’-deoxytubercidin, 2’-deoxyadenosine and related 2’-
`deoxynucleosidesvia a novel direct stereospecific serum salt gly-
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`13. Beutler E (1992) Cladribine(2’-Chlorodeoxyadenosine). Lancet
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`14. Liliemark J, Pettersson B, Juliusson G (1991) Determination of
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`Chromatogr 5: 262-264
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`
`Dr. F. Albertioni
`Departmentof Clinical Pharmacology
`Karolinska Hospital
`8-10401 Stockholm
`Sweden
`
`4
`
`