The Breast (1996) 5, 192—195
`© 1996 Pearson Professional Ltd
`
`ESO TASK FORCE ARTICLE
`
`Clinical studies with the specific ‘pure’ antioestrogen ICI 182780
`
`A. Howell, D. J. DeFriend*, J. F. R. Robertsonl, R. W. Blameyl, L. Anderson, E. Andersoni, F. A. Sutcliffe§ and
`P. Walton§
`
`CRC Department of Medical Oncology, University of Manchester, *Department of Surgery, University Hospital of South
`Manchester, 7Department of Surgery, City Hospital, Nottingham, §Zeneca Pharmaceuticals, Macclesfield, iTumour
`Biochemistry Laboratory, Christie Hospital, Manchester, UK
`
`S U M M A R Y. We have shown that ICI 182780 inhibits the growth of metastatic tumour cells derived from patients failing
`treatment with tamoxifen when grown in vitro. In this system tamoxifen stimulates growth of tumour cells which can be
`reversed by addition of ICI 182780 to tamoxifen in culture. In a phase I study we have demonstrated that treatment of
`patients for 7 days before surgical excision of the tumour resulted in marked down regulation of ER, inhibition of growth and
`oestrogen-induced gene expression. More recently we demonstrated that treatment of advanced breast cancer patients with
`ICI 182780, after tamoxifen failure, resulted in a high remission rate and prolonged periods of remission with very few side—
`effects. These data indicate that further clinical trials of ICI 182780 are warranted. We expect that it will show superiority
`over conventional endocrine therapy.
`
`DISCUSSION
`
`Tamoxifen was first used in the clinic in December 1969.1
`
`It rapidly became the endocrine therapy of choice for
`women with advanced breast cancer because, although no
`more active than endocrine therapies used at that time, it
`had fewer side effects. This feature together with beneficial
`agonist effects on bone and lipids has lead to its widespread
`use as adjuvant therapy after surgery for primary breast
`cancer and in clinical trial as a preventative agent in women
`at high risk. However, there is strong evidence derived from
`experiments with human mammary tumour cells grown in
`vitro as reported by Nicholson et al2 in this issue and in nude
`mice3 that tamoxifen may become an agonist with respect
`to tumour cells. Tumour agonism is also seen in the clinic,
`although uncommon, since withdrawal responses to tamo-
`xifen have clearly been demonstrated.4 Tumour regression
`after withdrawal of tamoxifen clearly suggests that, at the
`time of progression,
`tamoxifen was stimulating tumour
`growth and that response is due to removal of the ‘oestro-
`genic’ stimulus.
`In the mid-1980s scientists at Zeneca Pharmaceuticals
`
`(then ICI) considered that the development of oestrogen
`
`Address correspondence to: A. Howell, CRC Department of Medical
`Oncology, University of Manchester, Christie Hospital NHS Trust,
`Wilmslow Road, Manchester M20 4BX, UK
`
`antagonists without agonist activity — ‘pure’ or specific
`antioestrogens - might be of benefit clinically for control
`of hormone-dependent tumours and hormone-induced be—
`nign conditions such as endometriosis and benign breast
`disease. They might also provide more specific probes for
`understanding molecular mechanisms of hormone-receptor
`interactions.
`
`that synthesis of further triphenylethylene
`It was felt
`analogues of tamoxifen would not produce structures with
`suitable pharmacological profiles and a novel chemical ap-
`proach was necessary. The work of Baulieu’s groups identi—
`fied the C7-position of oestradiol as a point of attachment
`for long alkyl substituents which could produce specific
`antagonists without reducing the affinity of molecules for
`the oestrogen receptor (ER).
`A series of C7 analogues was tested in the immature rat
`uterus assay,6 the model which provides the simplest
`demonstration of a difference between partial agonists and
`specific antagonist antioestrogens. In the absence of oestra—
`diol, tamoxifen is a partial agonist and stimulates growth
`of the uterus. However,
`in the presence of oestrogens,
`tamoxifen partially reverses oestrogen-induced growth.
`Most of the non—steroidal antioestrogens in the clinic (i.e.
`tamoxifen, toremifene, raloxifene, droloxifene, TAT-59 and
`idoxifene) have more or less agonist and antagonist activity
`in this assay. The specific antioestrogens ICI 164384 and
`ICI 182780 (Fig. 1) act as complete antagonists of oestrogen
`
`192
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`InnoPharma Exhibit 1041.0001
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`
`Clinical studies with the specific ‘pure’ antioestrogen ICI 182780
`
`193
`
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`//(CH2)1oc0I\IKCH2)3CHa
`ICI 164,384
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`/// (CH2)QSO(CH2)3CF2CF3
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`ICI 182,780
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`Structures of the steroidal ‘pure’ antioestrogens ICI 164384 and
`Fig. 1
`ICI 182780.
`
`action and have no agonist activity in the absence of oestro-
`gen in the uterus assay.7 ICI 182780 was selected to
`enter the clinic as it has higher affinity for ER (equal to
`oestradiol) than the first lead compound (ICI 164384).
`The first clinical trial short-term administration of ICI
`
`182780 by daily administration before surgery for breast
`cancer is outlined by Anderson et 211.8 There was very little
`toxicity from daily injections of ICI 182780 and even after
`short-term administration there was marked downregulation
`of ER and progesterone receptor (PR) and inhibition of pro-
`liferation. Thus, it was clear that ICI 182780 had antitumour
`
`effects in humans and the question then arose regarding the
`best clinical scenario to test for tumour regression. It was
`not clear that the compound should continue in develop-
`ment and a trial was required which would give the indica—
`tion of maximal compound potency whilst requiring as few
`patients in trial as possible.
`As ICI 182780 had been shown to inhibit the prolifera-
`tion of tamoxifen-resistant human mammary tumour cell
`lines when grown in vitro or in nude mice, it was decided
`to test the compound in women with advanced breast cancer
`who had failed tamoxifen therapy given either as an
`adjuvant at initial diagnosis or given for advanced disease.
`Because there was no guarantee of response, and it was an
`unusual study of sequential use of two antioestrogens, we
`
`selected patients likely to respond to therapy. They had to
`have failed on adjuvant tamoxifen given for 2 or more
`years, or, when given for advanced disease the patients must
`have had a complete or partial reponse to tamoxifen, or
`remained stable, for at least 6 months. Nineteen patients
`matched these criteria and were recruited in Manchester
`
`and Nottingham between 11 November 1992 and 2 June
`1993.
`
`Before beginning the trial we wished to determine whether
`‘primary’ human tumours were stimulated by tamoxifen
`in a colony assay and,
`if so, whether such stimulation
`could be reversed by the addition of ICI 182780. Tumour
`cells from six pleural effusions in patients failing tamoxifen
`were plated in semi-solid agar without serum oestradiol or
`phenol red. Growth in four of the six was significantly
`stimulated by 10‘10 M oestradial and in two by 10‘8 M 4-
`hydroxytamoxifen (Fig. 2).9 Both the oestradiol and tamoxifen
`stimulation could be reversed by the addition of 104; M ICI
`182780. These data confirm that some primary tumours
`may be stimulated in vitro by tamoxifen at the time of clini~
`cal progression on the drug. The fact that stimulation could
`be reversed by ICI 182780 gave us confidence to initiate a
`clinical trial.
`At the time of these studies ICI 182780 was not con—
`
`sidered to be bioavailable in an oral form so a depot injec~
`tion was developed by dissolving the drug in a castor
`oil-based vehicle. As judged by inhibition of uterine prolif-
`eration in adult female monkeys it was predicted that serum
`levels in excess of 2—3 ug/ml would be sufficient to produce
`a therapeutic effect
`in patients with advanced breast
`cancer.10 It was found that levels of ICI 182780, using a
`250 mg depot, reached a peak of 7.5 ng/ml during the first
`8 days of treatment and at 28 days there was still a mean of
`3 ng/ml. During the sixth monthly cycle there was evidence
`of accumulation of the drug such that the level at 28 days
`had a mean of 6 ng/ml. Thus, levels above the minimum
`therapeutic levels were attained.
`Full details of the study will be published shortly.‘ How-
`ever, in summary, of the 19 patients treated, 7 (37%) had a
`partial response and a further 6 (32%) stabilization of their
`disease for more than 6 months. The median duration of
`
`response has just been reached and is 25 months. Five
`patients remain in remission for 30+, 30+, 32+, 33+ and 33+
`months respectively. When we looked at a matched group
`of women from our database with the same favourable char—
`
`acteristics, treated with megestrol acetate, the response rate
`was 60% (PR + no change) but the median duration of
`remission was only 14 months. Thus, not only do patients
`respond to steroidal antioestrogen after failure on a non-
`steroidal compound (tamoxifen) but the duration of response
`appears twice as long. These conclusions are, of course,
`tentative and will need confirmation in further clinical trials.
`It is of interest that treatment of MCF—7 tumours in nude
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`InnoPharma Exhibit 1041.0002
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`Fig. 2 Responses of cancer cells from 6 clonogenic pleural effusions to oestradiol (E2), 4~hydroxytamoxifen (4
`OHT) and ICI 182780. Columns show CFE’s as percentages of the control CFE for each effusion. Reproduced
`by the kind permission of Stockton Press from DeFriend et al. Br J Cancer 1994; 70: 204—211.
`
`mice with ICI 182780 produced tumour control for twice as
`long as tamoxifen, as reported by Osborne.3
`There have been no major side effects with ICI 182780
`up to the maximum treatment period to date (November
`1995) of -33 months. In View of the degree of oestrogen
`suppression, as judged by very low or undetectable ER
`levels shown in the tumours of women in the phase I study,
`we anticipated inducing hot flushes and hot sweats. How-
`ever, if hot flushes were present prior to the trial they were
`not increased and none were induced. LH and FSH levels
`
`were initially low for postmenopausal women, presumably
`related to treatment with tamoxifen. During treatment both
`hormones rose to levels in the middle of our normal range
`and not the high levels expected if all effects of oestrogen
`were removed from the hypothalamus and pituitary gland.“
`The apparent lack of effect of ICI 182780 on the hypo-
`thalamus suggests that the molecule might not pass the
`blood brain barrier.
`
`In rats oestrogen not only controls gonadotrophin secre-
`tion during the menstrual cycle but also reduces food intake
`and decreases body weight. Tamoxifen has a similar effect
`to oestrogens but there was no change of food intake with
`ICI 164384, ICI 182780 and a specific non-steroidal anti-
`oestrogen ZM 189154.‘2 Again these data support the sug-
`gestion that the specific antioestrogens fail to penetrate the
`blood brain barrier. The selective action of ICI 182780 was
`
`confirmed by Wade et al13 who demonstrated that [3H]
`oestradiol uptake in the rat was blocked by tamoxifen in
`all target tissues including the brain but treatment with ICI
`182780 failed to block uptake at this site. Experiments in
`vitro with brain-derived ER showed tight binding of ICI
`
`182780 further suggesting that lack of binding in vivo was
`related to inability of the molecule to cross the blood brain
`barrier.
`
`We expected to find patients complaining of vaginal
`dryness during treatment with ICI 182780 but again, sur-
`prisingly, this was not reported by any of the 19 patients,
`even after prolonged treatment periods. Serial uterine
`ultrasound measurements were performed in five patients.
`All had endometrial ‘thickening’ compatible with a partial
`agonist effect produced by previous treatment with tamo-
`xifen but
`there was no increase on treatment with ICI
`
`182780 over periods of up to 15 months. We expected to
`detect a decline in endometrial thickness but were reassured
`
`there was no further increase suggesting an antioestrogenic
`effect of ICI 182780 on the uterus. The stabilizing effect on
`the endometrium was seen also in short-term studies where
`
`ICI 182780 was given for 7 days before hysterectomy in
`premenopausal women” and after longer term administra—
`tion in adult female monkeys.10
`Sex hormone binding globulin (SHBG) levels tended to
`be high at the beginning of treatment and declined during
`therapy with ICI 182780. Serum cholesterol, triglycerides
`and high and low density lipoprotein cholesterol were
`unchanged with up to 15 weeks of treatment with ICI
`182780.“ The SHBG and lipid data are difficult to interpret.
`A fall in SHBG suggests that this was due to either removal
`of the oestrogenic effect of tamoxifen or an antioestrogen
`effect of ICI 182780 on the liver. If the latter, serum lipid
`levels should have risen but they remained stable throughout
`the period of study. Further work is necessary to delineate
`the effect of ICI 182780 on the human liver.
`
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`Clinical studies with the specific ‘pure’ antioestrogen ICI 182780
`
`195
`
`One of the major concerns regarding a new antioestrogen
`in women is the potential for a negative effect on bone. As
`patients in the phase II study had advanced breast cancer,
`bone density measurements were not made. Initial observa—
`tion in normal adult female rats showed that ICI 182780 had
`
`no effect on bone whilst showing the expected inhibitory
`effect on the uterus.15 However, more recent histomorpho—
`metric studies have demonstrated an oophorectomy—like ac-
`tion of ICI 182780 on tibial cancellous bone volume in intact
`
`rats.16 In this study a 20% reduction in cancellous bone vol-
`ume was reported. The reason for the discrepancy between
`the two studies is not clear. It will be important to perform
`careful bone density studies in future trials of ICI 182780. It
`is possible that in humans ICI 182780 will be peripherally
`selective with respect to bone at the final dose used. Recent
`studies with a specific (‘pure’) non-steroidal antioestrogen
`in immature rats showed no effect on bone at doses which
`
`produced maximal uterine atrophy; whereas five times the
`dose reduced bone density, although to a lesser extent than
`oophorectomy.12
`
`Acknowledgement
`
`The European School of Oncology gratefully acknowledges an educational
`grant from Zeneca Pharmaceuticals which made the meeting possible.
`
`References
`
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`. De Friend D, Anderson E, Bell J, Wilks D P, West C M L, Howell
`A. Effects of 4—hydroxytamoxifen and a novel pure antioestrogen
`(ICI 182780) on the clonogenic growth of human breast cancer cells
`in vitro. Br J Cancer 1994; 70: 204—211.
`Dukes M, Waterton J C, Wakeling A E. Antiuterotrophic effects of
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`Dukes M, Chester R, Yarwood L, Wakeling A E. Effects of non-
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`182780 reduces cancellous bone volume in female rats.
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`16.
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