CENTER FOR DRUG EVALUATION AND RESEARCH
`
`APPROVAL PACKAGE FOR:
`
`APPLICATION NUMBER
`
`21-344
`
`Pharmacology Review(s)
`
`

`

`Pharmacology/Toxicology Review of NDA 21-344
`
`Date:
`
`5 Mar. 2002
`
`From:
`
`David E. Morse, PhD.
`
`Supervisory Pharmacologist
`Div. of Oncology Drug Products, HFD-ISO
`
`To:
`
`Robert Temple, MD.
`Director, Office of Drug Evaluation 1
`
`Through:
`
`Richard Pazdur, MD.
`Director, Div. of Oncology Drug Products, HFD—lSO
`
`Cc:
`
`Subject:
`
`Grant Williams, M.D., Dep. Dir., DODP (HFD-l 50)
`Lilliam A. Rosario, Ph.D., Pharrn./Tox., DODP (HFD-lSO)
`
`NDA 21-344
`FASLODEX®® Injection (fulvestrant)
`Secondary Review of Pharm/Tox. Information and Product Label
`
`1. Materials Included in Review
`
`1. Pharm/Tox. Review of NDA 21-344, written by Lilliam A. Rosario, Ph.D.
`
`II. Backgound
`
`The sponsor (AstraZeneca Pharmaceuticals, LP.) is seeking approval of FASLODEX®
`(injection) for use in
`Df‘a ff
`-—————-—-
`'
`~
`
`FASLODEX® (fulvestrant) is a modified steroid, which binds competitively to the
`estrogen receptor (ER), with an affinity approximately comparable to that of estradiol.
`Fulvestrant acts as a competitive inhibitor of the activation of the ER by estradiol, and
`thereby inhibits the growth of ER+ dependent tissues.
`
`III. Comments and Conclusions
`
`1. A review of NDA 21-344, FASLODEX® Injection (fulvestrant), indicates the product has
`been adequately evaluated in multiple repeat-dose non-clinical safety studies (including:
`acute and repeat-dose (IM) toxicology studies up to 6 and 12 months in rats and dogs),
`reproductive toxicity tests in rats and rabbits (Segments l-III; ICH endpoints A-F),
`genotoxicity tests (in vitro and in vivo), and in two carcinogenicity bioassays (in mice and
`rats), for approval in the treatment of postmenopausal women with locally advanced or
`metastatic breast cancer who have previously been treated with endocrine therapy. It
`should be noted that the carcinogenicity testing and full spectrum of reproductive toxicity
`studies performed by the Sponsor were not deemed necessary by the Review Division for
`potential product use in a postmenopausal patient population with advanced neoplastic
`disease.
`
`

`

`2. Specific comments pertaining to the product review follow.
`
`Genotoxic and Carcinogenic Potentiat
`
`In a 2-year carcinogenesis study in rats (male and female), an increased incidence of
`benign ovarian granulosa cell tumors and testicular Leydig cell tumors was evident, in
`females dosed at 10 mg/rat/ 15 days and males dosed at 15 mg/rat/3O days, respectively.
`Induction of such tumors is consistent with the pharmacology-related endocrine feedback
`alterations in gonadotropin levels caused by an anti-estrogen. Fulvestrant showed no
`antigenic, mutagenic, or clastogenic potential in a standard battery of genotoxicity tests
`when evaluated at doses or concentrations appropriate to the assay.
`
`Following review of the carcinogenicity data by the Executive Committee of the CAC
`(Carcinogenicity Assessment Committee), it was recommended by the executive
`committee that the sponsor be asked to conduct a P32 post-labeling assay for the
`formation of DNA adducts by fulvestrant (or its’ metabolites). This request was
`apparently based on previous experience with tamoxifen (a related competitive inhibitor of
`the ER), which when tested for carcinogenic potential yielded positive results in multiple
`hormonally dependent tissues and caused an increased incidence of hepatic tumors (which
`could not be explained as dependent upon ER activity). When subsequently tested in the
`P32 post-labeling assay, it was found that exposure to tamoxifen resulted in the formation .
`of DNA adducts (a likely explanation for the increased incidence of hepatic tumors).
`
`As stated above, dosing with fulvestrant for up to 2 years resulted in an increased
`incidence of benign ovarian granulosa cell tumors and testicular Leydig cell tumors, in
`females dosed at 10 mg/rat/ 15 days and males dosed at 15 mg/rat/30 days, respectively.
`There was no evidence in the study of fulvestrant for the increased induction of tumors in
`any non-hormone dependent/sensitive tissue. Furthermore, fulvestrant showed no
`mutagenic or clastogenic potential in a standard battery of genotoxicity tests. Based on
`this data, it does not appear that further testing of the genotoxic potential of fulvestrant is
`necessary for product approval.
`
`Mechanism of Action:
`
`Fulvestrant binds ER in a competitive manner, with a high affinity comparable to that of
`estradiol. The Sponsor claims that “Fulvestrant is a potent antiestrogenic agent, which
`acts by down-regulation of the estrogen receptor (ER) inducing a rapid loss of ER protein
`from breast cancer cells. Preclinical studies demonstrated that fulvestrant is a potent,
`reversible inhibitor of the growth of estrogen- sensitive human breast cancer cells and of
`tamoxifen- resistant breast cancer cells in vitro. The sponsor appears to be intending to
`use this data as support for defining fulvestrant as a new class of antiestrogen, one that acts
`via a new mechanism. However, several issues, which should be considered as part of this
`topic, are outlined in the following paragraphs.
`
`A) In a study by Robertson et. a]. (2001), it was found that immune-reactive ER
`was reduced in tissues taken from postmenopausal women with breast cancer,
`who were treated with either fulvestrant or tamoxifen prior to surgery. While
`the dosing interval was limited in duration, this data does not appear to
`support the sponsor’s contention that fiilvestrant functions via a new and
`unique mode of action (dissimilar to the mode of action of tamoxifen).
`
`

`

`B) Throughout the MOA studies conducted by the sponsor, ER protein levels
`were measured by an indirect immuno—reactive assay methodology, as
`compared to direct receptor isolation/purification and protein analysis.
`Furthermore, the sponsor did not provide affinity data for the specificity of the
`ER antibodies, or data for effects of conformational changes that might occur
`with bound fulvestrant, tamoxifen or estradiol, and how this might alter
`antibody binding to the ER. It is therefor recommended that the product label
`clearly specify that ER protein was measured via an immuno-reactive assay
`(vs. direct protein measurement).
`
`Taken together, these data do not appear to support the sponsors' contention that
`fulvestrant functions through a unique mode of action (i.e., ER protein down-regulation),
`which is independent of the mode of action of tamoxifen.
`
`3. Specific cements pertaining to the product label follow.
`
`A review of the draft product label suggests that it adequately reflects the non-clinical
`safety profile of fulvestrant injection.
`
`IV. Summary
`
`A review of the action package for NDA 21-344, FULVESTRANT® Injection, suggests
`that the product has been adequately evaluated in multiple non-clinical safety studies for
`potential approval in the t
`—’
`—-——'
`There
`are no unresolved issues or requests to be directed to the sponsor for this indication.
`
`APPEARS THIS WAY
`0N ORIGINAL
`
`

`

`This is a representation of an electronic record that was signed electronically and
`this page is the manifestation of the electronic signature.
`
`/S/
`
`David Morse
`4/22/02 12:52:35 PM
`PHARMACOLOGIST
`
`

`

`PHARMA COLOGY/I‘OXICOLOGY COVER SHEET
`
`Executive Summary
`
`Recommendations
`
`A. Recommendation on Approvability: The non-clinical studies adequately support the
`use of fulvestrant (FASLODEX), by the intramuscular route, for
`‘ a
`—
`
`B. Recommendation for Nonclinical Studies: None
`
`C. Recommendations on Labeling: Please refer to Appendix B on page for 144 for
`labeling recommendations on the Carcinogenesis, Mutagenesis, Impairment of
`Fertility, Pregnancy, Nursing Mothers, and Warning sections of the product label.
`
`Summary of Nonclinical Findings
`
`A. Brief Overview of Nonclinical Findings
`
`Multiple non—clinical toxicity studies of up to 6 and 12 months duration in rats and
`dogs, genotoxicity, carcinogenicity, antigenicity, and local tissue irritancy effects were
`submitted to support the use of fulvestrant (IM) in the treatment of locally advanced
`and metastatic breast cancer in post-menopausal women.
`
`The high doses used in the long-term studies in rats (10 mg/rat/ 15d for 6 months) and
`dogs (40 mg/kg/28d for 12 months), based on body surface area conversion were
`approximately 4 fold higher than the proposed clinical dose of 250 mg/month. Drug
`exposure (AUCoqg’ 30 days) ranged from 4-10 fold and Cmax ranged from 9-38 fold
`higher in the longest duration toxicology studies than the values observed in clinical
`testing.
`
`Fulvestrant was well absorbed and widely distributed following IM administration in
`rats. Metabolism was qualitatively similar in rats, dogs, and human with the primary
`route of elimination in feces. Fulvestrant crosses the placenta following single
`intramuscular doses of 6.0 mg/m2 in rats and 3 mg/m2 in rabbits resulting in fetal
`tissue drug concentrations 2 hours afier dosing of 76 and 97% compared to maternal
`plasma, respectively. Fulvestrant is found in rat milk at levels significantly higher
`than in rat plasma (12-fold afier administration of 12 mg/mz). The maximal drug
`exposure in rat pups from ICI 182,780-treated lactating dams was estimated as 10.3%
`of the administered dose.
`
`In all the inn'amuscularly dosed toxicology studies, effects upon the reproductive tract
`and other organs sensitive to estrogens were observed, consistent with the proposed
`mechanism of action of fulvestrant. In female rats and dogs, atrophy of the uterus,
`cervix, and vagina with a loss of normal cyclical estrous activity was observed. In the
`ovary increased late stage and cystic Graafian follicles, loss of mature corpora lutea,
`
`

`

`and reduced vacuolation of the interstitial cells were observed. There was some
`
`evidence of reversibility of these ovarian changes (but not complete recovery)
`following dose cessation up to 20 weeks duration. In male rats, afier 6 months dosing,
`a loss of spermatozoa from the seminiferous tubules, seminiferous tubular atrophy,
`and degenerative changes in the epididymides were seen. There was an incomplete
`recovery of changes in the testes and epididymides after a 20-week recovery period.
`
`In female rats, fileestrant (20.06 mg/mz/day) administered prior to mating and until
`day 7 of gestation, caused a reduction in female fertility and embryonic survival. No
`adverse effects on female fertility and embryonic survival were evident in female
`animals dosed at 0.006 mg/mzlday. Restoration of female fertility was evident
`following withdrawal of dosing at 12 mg/mZ/day. Further, a dose of 12 mg/mZ/day
`during organogenesis resulted in maternal vaginal bleeding, and delay and
`prolongation of parturition in rats. There was an increase incidence of post-
`implantation loss in rabbits receiving levels of 23 mg/mz/day during organogenesis.
`
`Fulvestrant caused an increased incidence of fetal abnormalities in rats. Tarsal flexure
`of the hindpaw at 12 mg/mz/day and non-ossification of the odontoid and ventral
`tubercle of the first cervical vertebra at doses 2 0.6 mg/mzlday were observed when
`fulvestrant was administered during the period of organogenesis. Fulvestrant also
`caused an increased incidence of fetal abnormalities in rabbits (backwards
`displacement of the pelvic girdle, extra 13th ribs, and 27 pre-sacral vertebrae at 3
`mg/mz/day) when administered during the period of organogenesis. This study in
`rabbits was considered inadequate to fully define possible adverse effects on fetal
`development due to the lack of maternal toxicity at the highest dose (3 mg/mz/d) and
`incomplete fetal assessment at the low and intermediate doses tested.
`
`Fulvestrant showed no antigenic, mutagenic, or clastogenic potential. However, in a
`2-year carcinogenesis study in female and male rats, an increased incidence of benign
`ovarian granulosa cell tumors and testicular Leydig cell tumors was evident, in
`females dosed at 10 mg/rat/l 5 days and males dosed at 15 mg/rat/30 days,
`respectively. Induction of such tumors is consistent with the pharmacology—related
`endocrine feedback alterations in gonadotropin levels caused by an anti-estrogen.
`
`B. Pharrnacologic Activity
`
`Pharmacology studies show that fulvestrant binds to estrogen receptors in a competitive
`manner, with affinity comparable with that of estradiol. The drug’s mode of action
`appears to lead to downregulation of estrogen receptor protein. Fulvestrant is a reversible
`inhibitor of the growth of estrogen-sensitive human breast cancer (MCF-7) cells and
`tamoxifen-resistant MCF-7 cells in vitro. Fulvestrant blocks the uterotropic actions of
`endogenous and exogenous estrogens in rodents and monkeys, and of tamoxifen in the
`rat. In a series of in vivo xenograft studies, fulvestrant prevents the establishment of
`tumors from xenografls of human breast cancer (MCF-7) cells in nude mice, inhibits the
`growth of established estrogen-sensitive MCF-7 xenografis and-inhibits the growth of
`tamoxifen—resistant breast tumors.
`
`

`

`C. Nonclinical Safety Issues Relevant to Clinical Use:
`
`The Sponsor’s description of the mechanism of action of fulvestrant is adequately
`supported by the data submitted. However, it is noteworthy that both in vitro (Brunner et
`al., 1997) and in viva (Osborne et a1. 1995), it has been shown that tumors which
`eventually develop resistance to fulvestrant will not subsequently respond to tamoxifen.
`Thus, a treatment sequence in which ICI 182,780 precedes tamoxifen may not be
`indicated. It is recommended that this information be included in the label since it has
`
`repercussions for indications in which patients may be treated first with fulvestrant.
`
`In meeting to discuss the carcinogenic potential of Fulvestrant (December 4, 2001 ), the
`Executive Carcinogenicity Assessment Committee noted that while fulvestrant appears to
`have a negative profile for genotoxicity potential on a standard battery of tests, the
`Sponsor did not perform all of the defining studies (similar to Tamoxifen) to determine
`fulvestrant is not genotoxic. The Committee recommended that the Sponsor be asked to
`perform 32P post-labeling study to determine if fulvestrant and/or its’ metabolites may
`form adducts with cellular DNA. We agree that a 32P post-labeling study will be valuable
`in assessing possible genotoxic potential of Fulvestrant. However, given that the current
`indication for Fulvestrant ,
`_
`1) raft
`-—-——-'_-—
`, the request for this study may be postponed. If the indication for
`Fulvestrant was to change to include any other population, the Sponsor is strongly
`recommended to conduct a 32F post-labeling study to ensure that Fulvestrant is non-
`genotoxic.
`\
`
`Administrative
`
`\
`
`A. Reviewer signature:
`
`B. Supervisor signature:
`
`
`Lilliam A. Rosario PhD.
`Pharmacology-Toxicology Reviewer
`
`
`Concurrence — David Morse PhD.
`Supervisory Pharmacologist
`Non-Concurrence —
`(see memo attached)
`
`\
`U)
`5
`
`C. cc: list:
`
`brossp
`morsed
`
`rosan'ol
`
`

`

`PHARMA C0LOG Y/TOXICOLOG Y COVER SHEET
`
`NDA number:
`
`Review number:
`
`21,344
`
`1
`
`Sequence number/date/type of submission: 000/3-28-2001/NDA
`
`Information to sponsor: Yes (x) No ( )
`Sponsor:
`IPR Pharmaceuticals, Inc
`1800 Concord Pike P 0 Box 8355
`
`Wilmin
`
`g’ton, DE 19803—8355
`
`Manufacturer for drug substance :
`
`US Agent:
`AstraZeneca Pharmaceuticals LP
`1800 Concord Pike P 0 Box 8355
`
`Wilmington, DE 19803-8355
`
`AstraZeneca UK Limited
`
`Silk Road Business Park
`Macclesfield Cheshire SK10 2NA UK
`
`Reviewer name:
`
`Division name:
`HFD #:
`
`Review completion date:
`
`Drug:
`
`Trade name:
`
`Generic name:
`
`Code name:
`
`Chemical name:
`
`Lilliam Rosario, Ph.D.
`
`Oncology Drug Products
`HFD-l 50
`
`December 20, 2001
`
`Faslodex
`
`Fulvestrant
`
`ICI 182,780, ZD9238
`
`7a-[ 9-( 4, 4, 5, 5, 5- pentafluoropentylsulfinyl)
`nonyl] estra-l,3,5( 10) triene- 3, l7B-diol.
`129453-61—8
`
`CAS registry number:
`Mole file number:
`
`Not provided
`Molecular formula/molecular weight: C32H47F503S / 606.8
`Structure:
`
`OH
`
`HO
`
`“’IqCHg,SO{CH,\30gCF3
`
`Relevant INDs/DMFS: IND - ,DMF‘ DMFa— DMF "DMF ~i-
`
`Drug c1 ass: Anti-estrogen
`
`

`

`15m 4%
`
`‘ A
`
`Indication: FASLODEX is indicated for i
`
`Clinical formulation:
`
`Qualitative composition of FASLODEX
`Table 2
`
`
`
`
` Ingredient Function Reference to standards
`
`
`
`Fulvestrant
`Alcohol
`
`Drug substance
`we
`
`See ‘Specification of the Drug Substance’
`USP
`
`Benzyl alcohol
`
`"'
`
`USNF
`
`USP
`"
`Benzyl benzoate
`
`
`"'Castor oil USP
`
`Route of administration: Intramuscular (IM)
`
`Proposed use: FASLODEXTM is a sterile oily solution for deep intramuscular (IM) injection. It is
`presented in one 5 ml or two 2. 5 ml pre-filled syringes to deliver, as a long acting (LA) injection,
`the required dose of 250 mg over a 1 month period. FASLODEX contains 50 mg/ml fulvestrant
`and is administered once monthly.
`
`Disclaimer: Tabular and graphical information is from sponsor’s submission unless stated
`otherwise.
`
`

`

`
`
`Reviewer: Lilliam A. Rosario PhD. NDA No.21-344
`
`TABLE OF CONTENTS- PHARMACOLOGY/TOXICOLOGYREVIEW
`
`II.
`
`111.
`
`VI.
`
`VII.
`
`PHARMACOLOGY: ...................................................................................................... 7
`
`SAFETY PHARMACOLOGY: ................................................................................... l6
`
`PHARMACOKINETICS/TOXICOKINETICS: ....................................................... 20
`
`GENERAL TOXICOLOGY: ....................................................................................... 34
`
`GENETIC TOXICOLOGY: ........................................................................................ 75
`
`CARCINOGENICITY: ................................................................................................ 89
`
`REPRODUCTIVE AND DEVELOPMENTAL TOXICOLOGY: ......................... 108
`
`APPENDIX/ATTACHMENTS: ................................................................................ 141
`
`APPEARS THIS WAY
`ON ORIGINAL
`
`vi
`
`

`

`
`
`Reviewer: Lilliam A. Rosario PhD. NDA No.21 -344
`
`PHARMA COLOGY/TOXICOLOGY RE VIEW
`
`1.
`
`PHARMACOLOGY:
`
`Primary pharmacodynamics:
`Mechanism of action:
`
`The Sponsor claims that “Fulvestrant is a potent antiestrogenic agent, which acts by
`downregulation of the estrogen receptor (ER), a mechanism that induces a rapid loss of
`ER protein from breast cancer cells. Fulvestrant binds ER in a competitive manner, with
`a high affinity comparable to that of estradiol. Preclinical studies demonstrated that
`fulvestrant is a potent, reversible inhibitor of the growth of estrogen- sensitive human
`breast cancer cells and of tamoxifen- resistant breast cancer cells in vitro. Fulvestrant
`
`prevents the establishment of tumors from xenografts of human breast cancer cells in
`nude mice, inhibits the growth of established estrogen- sensitive xenografts and inhibits
`the growth of tamoxifen- resistant breast tumors in vivo. Fulvestrant is a non- agonist
`antiestrogen which blocks the uterotrophic action of estradiol in mice, rats and monkeys
`without itself having any partial agonist estrogen- like activity. In studies with immature
`female rats, fulvestrant blocked the uterotrophic action of estradiol and the estrogenic
`(partial agonist) effect of tamoxifen.”
`
`Drug activity related to proposed indication:
`
`0 Downregulation of the estrogen receptor (ER) inducing a rapid loss of ER
`protein from breast cancer cells (from review Wakeling, 2000).
`“ "In contrast to the partial agonists, studies of the mode ofaction ofthe pure antioestrogens, ICI
`164384 and 1C] 1 82 780, have produced a consensus that the ability ofthe ER to activate or
`inhibit transcription in a ligand-dependent or -independent manner in vivo is completely
`attenuated by ICI 164354 and ICI 182780 (Wakeling I 995). Multiple changes in ER fimction
`following pure antioestrogen treatment appear to contribute to this complete abrogation of
`oestrogen action (see Fig. 3). These include impaired dimerisation (Fawell et al. 1990, Chen et al.
`1999), increased receptor degradation (Dauvois et al. 1992, Nicholson et al. 1995, Borras et al.
`1996, Pink & Jordan 1996) and disrupted nuclear localisation (Dauvois et al. 1993, Htun et al.
`1999). The rapid loss (down-regulation ’) ofER following ICI 164384- or 1C] 182 780-treatment
`ofcells in culture (Dauvois et al. 1992, Nicholson er al. 1995, Borras er al. 1996, Pink & Jordan
`1996), orfrom the uterus after in vivo treatment (Gibson et al. 1991), is likely to play a major role
`in abrogating oestrogen action. ER down-regulation would accountfor the ability ofpure
`antioestrogens to block the activation ofER by other mediators such as dopamine, CAMP and
`growth factors (Aronica & Katzenellenbogen 1993, Ignar—Trowbridge et al. I 993, Smith et al.
`1993, Newton et al. 1994, El-Tanani & Green I99 7) "
`"...As a consequence ofthe down-regulation ' ofER by ICI 164384 or [Cl 182 780, the
`transcription ofER-regulated genes should be completely blocked. This has proved to be the case
`in cells, in animal models, and in man. In the rat uterus, oestradiol and tamoxifen stimulate the
`expression ofa number ofgenes, including complement component C3 (GaIman et al. 1990),
`calbindin-D (Blin et al. 1995), IGF—I (Huynh Bc Pollack 1993), and vascular endothelial cell
`growth factor and c—fos (Hyder et at. l 997). In each case, ICI 164384 or ICI l 82 780 showed no
`induction oftranscripttion and, when adminstered with oestradiol or tamoxifen, completely
`blocked oestrogen or tamoxifen induction ofthese genes. Similarly. these two compounds act as
`pure anti- oestrogens on the transcription ofoestrogen inducible genes in human breast cancer
`cells in vitro (May et al. 1989, Wise. man et al. 1989, Nicholson et al. 1995), in viva (Osborne et
`al. 1995), and in patients with breast cancer (DeFriend et al. 1995)
`
`

`

`
`
`Reviewer: Lilliam A. Rosario Ph.D. NDA No.21-344
`
`
`
`Displacement
`curves
`
`0
`
`Flow cytometric
`analysis of cell
`cycle and
`population
`distribution of
`
`
`
`
`
`ICso 1C1 182, 780 =9.35 x10'9M; ICso Estradiol=8.32 x 10‘9 M
`Estrogen
`
`receptor
`0 Relative Binding Affinity (RBA) ICI 182.780 = 0.89 compared to estradiol RBA=1; RBA
`
`RBA from the
`
`
`binding
`tamoxifen= 0.025 (Wakeling and Bowler, 1988).
`
`
`rat uterus
`
`
`o
`ICI 182,780 is a competitive inhibitor of estradiol binding to ER (Wakeling et a1, 1991)
`
`
`o The RBA of ICI 182,780 for ER was similar to that of estradiol (0. 89 cf estradiol = l) and
`
`exceeded that of tamoxifen b a - troximatel 35-fold.
`
`
`
`
`
`Inhibition of
`MCF-7 (ER
`o
`ICI 182,780 inhibited the growth of MCF-7 cells in a concentration dependent manner (mean
`breast cancer
`IC50 3.1 x 10 '10 M from 7 experiments).
`
`positive) and BT
`
`
`
`. Estradiol (10 "° -10 ‘8 M) reversed the growth inhibitory effect of 10 '3 M ICI 182,780 in a dose-
`20 (ER negative)
`cell growth
`
`
`
`
`cell growth
`dependent and complete manner.
`
`
`
`inhibition.
`
`ICI 182,780 was more potent than ICI 164,384 (non-agonist antiestrogen; ICso values 0.3 vs 1.6
`
`
`x 10 '9) or 4- hydroxytamoxifen or tamoxifen (partial agonist antiestrogens).
`
`
`. BT 20 cells were unaffected by ICI 182,780 (10''0 to 10" M).
`
`
`
`o
`ICI 182,780 was not cytotoxic at a concentration IOOO-fold greater (1 x 10'5 M) than that
`
`
`
`required for full antiestrogenic activity (1 x 10'8 M).
`
`
`
`o The maximum reduction in cells with ICI 182,780 or ICI 164,384 =80%; tamoxifen or 4-
`
`
`
`
`o The Sponsor cites studies showing that tamoxifen-resistant cells remain sensitive to the growth
`inhibitory effect of ICI 182,780 (Brunner et a1, 1993; Hu et a1, 1993; Wiseman et a1, 1993;
`Lykkesfeldt et al, 1994), whereas ICI 182,780-resistant cells are cross resistant to tamoxifen
`(Brunner et al, 1997).
`It is important to note that given the cross resistance to tamoxifen, tumors which have relapsed
`during ICI 182,780 treatment may not respond to treatment with tamoxifen, thus, this treatment
`se-uence is not indicated.
`
`
`
`
`o
`
`MCF-7 cells.
`
`
`
`
`
`
`
`
`
`
`
`hydroxytamoxifen= 50%.
`0 Analysis of the population distribution of MCF-7 cells after 5 days of exposure to the tamoxifen
`or ICI 182,780 showed that in tamoxifen-treated cells, the proportion which continued to
`synthesise DNA was reduced from 82% (control) to 37%, whereas in ICI 182,780-treated
`cultures, this was reduced to 7 %.
`
`
`
`
`
`
`
`
`
`
`

`

`
`
`Reviewer: Lilliam A. Rosario Ph.D. NDA No.21-344
`
`grafts of the
`MCF-7 human
`
`breast cancer
`
`cell line, or from
`
`
`
`
`
`
`
`Anti- tumor
`Anti tumor
`0
`Single sc injection of 5 mg of ICI 182,780 blocked the growth of MCF-7-derived human breast
`
`
`effects
`tumor xenografls in nude mice for at least 4 weeks.
`
`
`
`activity in mice
`(Values are mean percent t SEM. n 2 S. oftumor arcs normalised by reference to the initial area
`bearing tumors
`
`
`
`of each lumor preceding the 4-week treatment period)
`derived from
`
`
`
`Trenmtem Wack2 Week]Wig-kl Week 4
`
`
`
`
`
`INXIO
`148129
`Control
`Ill! 19
`
`
`
`Tmmxil‘cn
`86 18
`7818
`sass
`
`
`
`8714
`9018
`7414
`ICI 182.780
`
`
`
`
`
`
`o The magnitude of this effect was comparable with that in animals treated daily with a high dose
`
`
`
`
`of tamoxifen (10 mg/kg/day po).
`
`0 The growth of transplants of the Br] 0 human breast tumor was suppressed by ICI 182,780
`
`
`
`Br10 (Ref
`treatment. A single sc injection of 5 mg of ICI 182,780 on the day of tumor implantation,
`
`
`
`Wakeling et al
`reduced tumor growth compared with controls. This effect was comparable with continuous
`
`
`
`1991).
`daily treatment with tamoxifen (10 mg/kg/day po) for 8 weeks.
`
`
`
`
`(Values are mean 1 SEM tumor area mm2 (n = 6-8) for all tumors attaining measurable size by
`
`
`day 50 post-implantation),
`
`Control
`Tamoxifen
`lCl182.780
`Mmsuremmt day
`
`
`
`53
`I714
`38 I 7
`28 i S
`
`
`73
`37 4
`72 x lo
`35114
`
`80
`46 t 8
`861“)
`44110
`
`
`59 1 7
`87
`104125
`50112
`
`
`94
`661 7
`[14128
`58:1:16
`
`
`
`OVARIECTOMY
`
`l 15
`95125
`6319
`6012i
`
`
`
`
` The Sponsor cites studies showing that ICI 182,780 inhibits the growth of tamoxifen-stimulated
`MCF-7 tumors in nude mice (Osborne et al 1994).
`
`o The efficacy of tamoxifen and ICI 182,780 in the treatment of established MCF-7 derived
`
`tumors in nude mice, and in preventing the growth of tumors from grafts of MCF-7 cells was
`
`comared b Osborne et al 1995 . Established tumors were treated either b withdrawal of
`
`explants of the
`human breast
`
`tumor-derived
`
`solid tumor,
`
`
`
`
`
`
`
`
`

`

`NDA Noll-344
`Reviewer: Lilliam A. Rosario Ph.D.
`
`
`
`
`exogenous estrogen alone, or by estrogen withdrawal and addition of tamoxifen (daily sc 0.5
`
`mg) or ICI 182,780 (weekly sc 5 mg LA).
`
`ICI 182,780 suppressed the growth of established tumors for twice as long as treatment with
`
`tamoxifen or estrogen withdrawal.
`
`The median time to progression with estrogen withdrawal alone or with tamoxifen was 97 and
`
`104 days, respectively). The median time to progression with ICI 182,780 was 200 days.
`
`Tumor formation was delayed in ICI 182,780-treated mice compared to tamoxifen-treated mice.
`
`Tamoxifen delayed tumor growth in estrogen-treated mice for 2 months; tumors grew slowly or
`
`not at all in mice treated with [Cl 182,780.
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`
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`The tumors which eventually grew out in some ICI 182,780-treated mice were transplanted into
`new recipient mice and tested for cross-resistance to tamoxifen. These tumors grew
`independently of estrogen supplementation and in some mice tamoxifen slightly reduced tumor
`growth rate. Thus, most mice resistant to ICI 182,780 showed cross-resistance to tamoxifen.
`These results predict that tumors which eventually develop resistance to ICI 182,780 will not
`
`subsequently respond to tamoxifen.
`Using the mouse MXT M1. 7 mammary carcinoma, ICI 182,780 demonstrated superior efficacy
`
`oared with tamoxifen Parcz k and Schneider, 1996 .
`
`
`Uterotropic and Treatment
`Treatment with exogenous estradiol alone stimulates an up to 5-fold reproducible increase in the
`
`antiuterotropic
`effects on the
`wet weight of the uterus with maximum response after 3 days of dosing. The estrogenic potency
`
`
`activity in
`weight of the
`of ICI 182,780, measured by their uterotropic action, can be compared with estradiol. Similarly,
`
`
`immature rat
`uterus.
`a reduction of uterine weight, in animals treated concurrently with estradiol and test compounds,
`
`
`measures antiestrogenic activity.
`
`
`Treatment
`In immature rats, ICI 182,780 administered parenterally (2 mg/ kg sc) or orally (5 mg/ kg po)
`
`
`reduced the weight of the uterus below that in vehicle treated controls.
`ICI 182,780 had no tropic action on the immature rat uteri.
`
`The same dose(s) of ICI 182,780, when co- administered with a maximally stimulating dose of
`
`estradiol (0. 5mg), completely blocked the tropic action of estradiol in a dose- dependent and
`
`complete manner.
`The parenteral ED50= 0.066 mg/kg sc and the oral EDso was 0. 9 mg/kg.
`Tamoxifen, partial agonist, stimulated the growth of the immature rat uterus but to a lesser
`extent than did estradiol. The uterotropic action of tamoxifen was blocked in a dose-dependent
`and com nlete manner b co-administration of ICI 182,780.
`
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`
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`effects in
`
`neonatal rats on
`
`premature
`opening of the
`vagina.
`
`
`
`
`
`
`
`
`10
`
`

`

`
`
`Reviewer: Lilliam A. Rosario PhD. NDA No.21-344
`
`0
`
`0
`
`weight of the
`uterus.
`
`
`
`
`
`Estrogen agonists cause premature opening of the vagina and disrupts normal reproductive
`
`development in neonatal rats. Estradiol or tamoxifen treatment in the first week of life brought
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`forward the time at which the vagina opens, from ~ the fifth week of life to the second or third
`
`
`week. ICI 182,780 alone had no effect indicating a lack of estrogenic activity in this test.
`
`0 When co- administered with tamoxifen, ICI 182,780 blocked premature vaginal opening in 9 of
`
`
`13 rats.
`
`Treatment
`
`
`
`Uterotropic and
`ICI 182,780 alone did not promote any growth of the uterus.
`
`effects on the
`
`antiuterotropic
`0 When co-administered with estradiol, there was a dose- dependent and complete blockade of
`
`
`
`weight of the
`activity in
`estrogen-induced uterine growth (ICI 182,780 ED 50 = 0.07 mg/kg sc; 0.7 mg/kg po).
`
`
`
`
`mature
`uterus.
`
`
`Since many steroids administered parenterally in oil have a sustained duration of action, the
`
`
`
`ovariectomized
`
`effect of ICI 182,780, as a single sc bolus dose in arachis oil, was tested in ovariectomized rats.
`
`
`
`rat
`Assessment of
`
`
`0 Vaginal comification in ovariectomized, estrogen (0.5mg)~treated rats was blocked for more
`
`
`
`vaginal
`than 6 weeks by a single injection of 10 mg of ICI 182,780.
`
`
`
`comification
`
`
`Single 2.5 mg ICI 182,780 im injection blocked vaginal comification for ~ 4 weeks in
`
`
`ovariectomized rats treated daily with 0.5 mg of estradiol benzoate.
`o The Sponsor cites reports continuing thecomplete absence of estrogen-like effects of ICI
`
`182,780 on the rodent uterus (Wade et a1 1993; Branham et a1 1996; Dao et al 1996; Dipippo
`
`
`and Powers 1997; Pillai et a1 1999). For example, Wade et al (1993) showed that ICI 182,780
`
`
`has no uterotropic activity, blocked the uterotropic effect of tamoxifen and had no estrogenic
`
`
`effects on food intake, body weight or estrous behavior. Branham et a1 (1996) demonstrated that
`
`
`ICI 182,780 blocked tamoxifen-induced developmental toxicity associated with the estrogenic
`
`
`effect of tamoxifen on the rat uterus. Also, showed that ICI 182,780 does not affect postnatal
`
`uterine develoment in the rat.
`
`
`
`Treatment
`
`
`Uterotropic and
`ICI 182,780 alone did not promote any growth of the uterus.
`effects on the
`
`antiuterotropic
`0 When co-administered with estradiol, there was a dose- dependent and complete blockade of
`
`
`
`activity in
`estrogen- induced uterine growth (ICI 182,780 EDso = 0.36 mg/kg sc; >4 mg/kg po).
`
`
`
`
`mature
`ovariectomized
`
`
`mouse
`
`
`
`
`
`Antiestrogenic
`Treatment
`ICI 182,780 reduced the weight of the uterus in a dose-dependent manner (EDso ~ 0.12 mg/kg.
`
`effects in intact
`effects on the
`0 At the highest daily dose used in this study (1 mg/kg), involution of the uterus after 14 days
`
`
`
`female rats
`weight of the
`a roached that followin ovariectom 90% effect . The maximum involution of the uterus
`
`
`
`
`
`
`
`11
`
`

`

`
`
`Reviewer: Lilliam A. Rosario Ph.D. NDA No.21-344
`
`
`uterus.
`
`
`after 2 or 4 weeks treatment with ICI 182,780 was less than that in rats ovariectomized for a
`Effects on on
`
`
`similar period.
`
`cyclical vaginal
`0 Cyclical vaginal cornification was blocked partially (0.1 mg/ kg) or completely (0.3 mg/ kg), but
`
`
`
`cornification,
`body weight gain and plasma gonadotropin concentrations were largely unaffected by ICI
`
`
`
`body weight
`182,780 treatment. The anticipated increase in body weight gain, plasma LH and FSH and
`
`
`
`gain, serum
`decrease in plasma PRL clearly evident in ovariectomized rats, were not observed in ICI
`
`
`
`gonadotrophins
`182,780- treated rats.
`
`
`and bone den