Clinical and pharmacological background

• Microtubule stabilizing (and destabilizing) agents have relevant role in the treatment of breast cancer (and other tumors)

• They are natural compounds discovered serendipitously or in large-scale screens from plant, microbial, and marine sources

• Increased knowledge of the molecular bases of their mechanisms of action and tumor resistance has allowed rational approaches to the development of new analogues or chemotypes with innovative pharmacological and clinical properties

Why target microtubules?• Microtubules are key components of the cytoskeleton• Perform multiple basic cellular functions

(maintenance of cell shape, transport of vesicles, mitochondria throughout cells, cell signaling, cell division and mitosis)

• Fill the area from nucleus to plasma membrane• Their polymerization dynamics are tightly regulated both

spatially and temporally• At least 3 distinct binding sites for tubulin-targeting

drugs• Disruption of microtubule dynamics leads to mitotic

arrest and cell death

Structure and function of microtubulesand mechanism of action of tubulin-binding

agents

Mitotic chromosome

Centriole

Microtubules

Subunits

-tubulin

-tubulin

Mitotic center

(+) end

(-) end

Top view

Tubulin dimers

24 nm

8 nm

Microtubules

Taxanes(stabilizers)

Tubulin

Vinca alkaloids

(destabilizers)

Polymerization

Polymerization

From Morris PG & Fornier MN, 2008, modified

Effect of microtubule-targeting agents on cell cycle

ChromosomesMicrotubulesKinetochores

*Some chromosomes remain at spindle poles Jordan MA, et al. Nat Rev Cancer. 2004

Prometaphase

Anaphase

Metaphase withpaclitaxel*

Telophase

Metaphase withvinflunine*

Early metaphase

• The reduced dynamic movements of chromosomes reduces the tension on the kinetochores, centromeres and the conjoined chromosomes.

• These changes are associated with the blocking of mitosis at the metaphase–anaphase transition.

Effects of tubulin targeting drugs on cancer cells

Kavallaris M et al., Drug Resit Updat 4:392-401, 2001

MDR = multidrug-resistance phenotype; Pgp = P-glycoprotein; MRP = multidrug resistance-associated proteins; MAP = microtubule-associated proteins.

Antimitotic drugs bind to microtubules at diverse sites

Jordan Ma & Wilson L, Nat Rev Cancer 4:253-265, 2004

a | A few molecules of vinblastine bound to high-affinity sites at the microtubule plus end suffice to suppress microtubule dynamics. b | Colchicine forms complexes with tubulin dimers and copolymerizes into the microtubule lattice, suppressing microtubule dynamics. c | A microtubule cut away to show the interior surface is shown. Paclitaxel binds along the interior surface of the microtubule, suppressing its dynamics.

Taxanes in clinical uses

Paclitaxel Docetaxel

Indications:

• adjuvant treatment of breast cancer• locally advanced or metastatic breast cancer • locally advanced or metastatic NSCLC• hormone refractory metastatic prostate cancer• metastatic gastric adenocarcinoma• locally advanced squamous cell carcinom of the head & neck

Indications: • advanced ovarian cancer • adjuvant treatment of node positive breast cancer • metastatic breast cancer • advanced NSCLC • advanced AIDS-related Kaposi’s sarcoma From EMEA/FDA product information

Disadvantages of first-generation taxanes

• Poor bioavailability• Low solubility in water• Need of surfactant agents (cremophor

EL, Tween80) believed to be responsible for severe allergic reactions

• Relevant toxicity• Treatment failure due to intrinsic or

acquired multidrug resistance

Cellular changes associated with multidrug and taxane resistance

• Overexpression of members of the ATP-binding cassette family of drug transporters– eg, p-glycoprotein

• Alterations in microtubule/tubulins– Tubulin mutations– Overexpression of tubulin isotypes with more

dynamicity (-III)– Changes in the expression of microtubule-

associated proteins (MAPs)

Fojo AT, et al. 2005; Dumontet C, et al. 1999

Microtubule destabilizers and stabilizers

and their binding sites on tubulin

Morris PG & Fornier MN, Clin Cancer Res 22:7167-7172, 2008

MICROTUBULE DESTABILIZERS MICROTUBULE STABILIZERS

Vinca alkaloidsVincristineVinblastineVinorelbineVinflunine

Halicondrins(eribulin mesylate)CryptophycinsDolastatinsHemiasterlins

Vinca binding

site

Colchicine binding

site

Taxane binding

site

Laulimalide

binding site

Epothilones

Epothilone B

(Patupilone)

Epothilone D

(KOS-862)Combrestatins

Taxanes

2-MethoxyestradiolSulphonamides

• Dehydelone (KOS-1584)

LaulimalidePeloruside A

EleutherobinSarcodictyins A+BCyclostreptin

• Paclitaxel • Docetaxel• ABI-007• CT-2103• Taxoprexin• Larotaxel• Cabazitaxel

Ixabepilone Sagopilone BMS-310705

Colchicine

DiscodermolideDictyostatin

Natural-product microtubule-stabilizing agents and their sources

Agent Chemical structure

Source

Paclitaxel Diterpene Taxus brevifolia Pacific yew tree

Docetaxel* Diterpene Taxus baccata European yew tree

Epothilones Macrolides Sorangium cellulosum Myxobacterium

Discodermolide

Lactone Discodermia dissoluta Sponge

Dictyostatin Lactone Spongia sp Sponge

Eleutherobin Diterpene Eleutherobin aurea Coral

Sarcodictyns Diterpenes Sarcodictyon roseum Coral

Cyclostreptin Polyketide Streptomyces sp Actinobacterium

Laulimalide Lactone Fasciospongia rimosa/ Cacospongia mycofijiensis

Sponge

Peloruside A Polyketide Mycale sp Sponge

Taccalonolides Lactones Tacca plantagine/chantrieri

Plant

* semi-synthetic analogue from 10-deacetyl baccatin III

Summary of defined microtubule stabilizing agents

From Zhao Y et al., 2009, modified

MDR: Multi-drug resistance; P-gp: P-glycoprotein

Compounds Binding site Effect on MDR tumour cells

P-gp overexpression

-tubulin related factors

Paclitaxel, docetaxel

Taxol-binding site - -

Second/third generation taxanes

Taxol-binding site + +/-

Epothilones Taxol-binding site + +

Discodermolide Taxol-binding site or overlapped

+ +

Dictyostatin Same as discodermolide (probably)

+ +

Eleutherobin Taxol-binding site (probably) - -

Sarcodictyins Taxol-binding site (probably) + +

Cyclostreptin Taxol-binding site (irreversibly) + +

Laulimalide Laulimalide-binding site + +

Peloruside A The same or overlapped laulimalide-binding site, or a new site

+ +

New paclitaxel formulations

Name Compound Clinical stage

ABI-007 (Abraxane)

Nanoparticle-albumin bound paclitaxel

Approved (treatment of metastatic breast cancer in patients who have failed first-line treatment for metastatic disease and for whom standard, anthracycline containing therapy is not indicated)

Paclitaxel poliglumex (CT-2103, Opaxio, Xyotax)

Poly(L-glutamic acid)-paclitaxel Phase III trials for NSCLC and phase II trials for ovarian cancer reported

Docosahexaenoyl-paclitaxel (taxoprexin)

Docosahexaenoic acid (DHA)-conjugatedpaclitaxel

Phase III trials ongoing(treatment of NSCLC)Phase II trials for other cancers reported

nab-paclitaxel (ABI-007)• Paclitaxel bound to albumin nanoparticles • Advantages:

– Cremophor free formulation– Lower risk of hypersensitivity reactions– No premedications needed– Shorter infusion time– Linear, predictable PK– Greater amount of drug delivered to the target cells

• Might make use of gp60-albumin mediated receptor transport across endothelial cells

Morris and Fornier, 2008; Ibrahim et al., 2002; Desai et al Clin Cancer Res 2006

nab-paclitaxel

Trial No. ptsSettin

gSchedule

RR (%)

Med TTP (wks)

Ibrahim1 63 No limit300 mg/m2

Q3w48 27

Mirtsching2 23 1st line125 mg/m2 QW

(3 out of 4 wks)

57 NR

Gradishar3

nab-paclitaxel vs paclitaxel

225 vs 229 1st line260 mg/m2 vs. 175 mg/m2 Q

3W33 vs 19 23 vs 17

Significant differences in RR = response rate (p=0.001) and TTP= time to progression (p=0.006);

NR= not reported

1Ibrahim, JCO 2005; 2Mirtsching Breast Ca Res Treat Suppl 2006; 3Gradishar JCO 2005

Adverse events

Gradishar WJ et al., J Clin Oncol 23:7794-7803, 2005SD, standard deviation; ANC, absolute neutrophil count; * p<0.05

A) all grades reported in more than 20% of patients in either treatment group

B) grade 3 and 4 reported in ≥ 5% of patients in either

group

• The incidence of grade 4 neutropenia was significantly lower for ABI-007 compared with standard paclitaxel (9% vs 22%, p=0.001)• Grade 3 sensory neuropathy was more common in the ABI-007 arm than in the standard pazlitaxel arm (10% vs 2%, p=0.001) but was easily managed and improved rapidly (median 22 days)•No hypersensitivity reactions occurred with ABI-007 despite the absence of premedication and shorter administration time

• ABI-007 showed superior efficacy to paclitaxel in a phase III study in metastatic breast cancer.

• Although ABI-007 use was associated with less neutropenia, its use did increase the risk of peripheral neuropathy.

• ABI-007 is now approved by FDA and EMEA for the treatment of metastatic breast cancer.

• A phase II study of ABI-007 in combination with trastuzumab and carboplatin in patients with metastatic breast cancer is ongoing.

• An adjuvant phase II trial of doxorubicin and cyclophosphamide followed by ABI-007, all in combination with bevacizumab, for breast cancer patients has recently completed accrual.

• The incorporation of ABI-007 into standard taxane-based regimens could potentially remove the need for premedication with steroids and could allow more rapid infusion times.

nab-paclitaxel

Phase II study nab-paclitaxel vs. docetaxel

Comparisons Comparisons (N=300)(N=300)

nabnab-paclitaxel vs. -paclitaxel vs. docetaxeldocetaxel ( (A, B, CA, B, C vs.vs. D D))

weekly vs. every-3-weekly vs. every-3-weeks weeks nabnab-paclitaxel-paclitaxel ( (B, CB, C vs.vs. AA))

low vs. high dose low vs. high dose weekly weekly nabnab--paclitaxelpaclitaxel ((BB vs.vs. C C) )

Arm A: nab-paclitaxel 300 mg/m2 q3w(n=76)

Arm B: nab-paclitaxel 100 mg/m2

weekly 3 out of 4(n=76)

Arm C: nab-paclitaxel 150 mg/m2

weekly 3 out of 4(n=74)

Arm D: docetaxel 100 mg/m2 q3w(n=74)

RR

AA

NN

DD

OO

MM

II

ZZ

EE

first-line metastatic breast cancer patients randomized to 4 first-line metastatic breast cancer patients randomized to 4 arms:arms:

Arms A, C and D administered at the MTDArms A, C and D administered at the MTD

Gradishar W, et al. ASCO 2007. Abstract 1032.

Phase II study evaluating various doses of nab-paclitaxel vs.

docetaxelABX 300 mg/m2 q3w ABX 100 mg/m2 qw3/4ABX 150 mg/m2 qw3/4Docetaxel 100 mg/m2 q3w

P = .016

P = .007P = .003

P = .002100

90

80

70

60

50

40

30

20

10

0

Resp

on

se R

ate

(%

)

Treatment

43

62

n = 76 76 74 74

70

38

Gradishar W, et al. ASCO 2007. Abstract 1032.

Phase II study evaluating various doses of nab-paclitaxel vs. docetaxel

Months

Progression-free SurvivalInvestigator Assessments

Pro

port

ion

Not

Imp

roved

30 6 9 12 15 180.0

0.25

0.50

1.0

75% of patients off-study

0.75

AB CD

Gradishar W, et al. ASCO 2007. Abstract 1032.

• PFS statistically superior with 150 mg/m2 (P = .002) and 300 mg/m2 nab-paclitaxel (P = .046) compared with docetaxel in MBC

• PFS statistically superior with 150 mg/m2 nab-paclitaxel compared with 100 mg/m2 nab-paclitaxel (P = .009)

• Lower incidence of neutropenia and fatigue with all schedules of nab-paclitaxel compared with docetaxel

• Randomized phase III trial comparing weekly nab-paclitaxel 150 mg/m2 vs. docetaxel 100 mg/m2 in MBC planned

New taxanes in phase III clinical trials

Larotaxel (XRP9881, RPR 109881A) Cabazitaxel (XRP-6258, TXD258)

• Phase III trials completed for the treatment of breast and pancreatic cancer – results not yet published

• Phase III trials ongoing for the treatment of bladder cancer

• Favorable therapeutic index in taxane-pretrated metastatic breast cancer(Dieras V et al., 2008)

• A phase III trial completed in combination with prednisone for the treatment of hormone-refractory metastatic prostatic cancer

• Results recently published (ASCO GU 2010)

• Oral route

New taxanes in phase II trials

TPI-287 (NBT-287)Ortataxel

(BAY 59-8862/IDN5109)

Milataxel (MAC-321)

Tesetaxel (DJ-927)

Phase II trials ongoing for the treatment of pancreatic, prostate cancer and melanoma

Phase II trials ongoing for the treatment of NHL, NSCLC, breast, kidney, renal cell carcinomaOral route

Phase II trials ongoing for the treatment of colorectal, gastric cancer and melanoma. IV/Oral route

Phase II trials ongoing for the treatment of mesothelioma, NSCLC and colorectal cancerIV/Oral route

BMS-275183Phase II trials ongoing for the treatment of NSCLCOral route

New taxanes in phase I trials

Simotaxel (TL909) TL-310

BMS-184476BMS-188797

Chemical structures of the natural epothilones and the synthetic epothilones currently in

clinical development

Structural differences among the natural moieties are indicated with gray circles. Within epothilone B and D derivatives, structural differences from natural epothilones are indicated using gray ellipses. From Michaud LB, Ann Pharmacother 43:1249-309, 2009, modified

Natural epothilones

Epothilone A Epothilone B(Patupilone)

Epothilone C Epothilone D(KOS-862)

Ixabepilone(Aza-epothilone B)

Sagopilone(ZK-EPO) BMS 310705

Semi- & FullySynthetic Derivatives

Dehydelone KOS-1584

Epothilones: mechanism of action

• Induce microtubule stabilization– Bind to -tubulin– Compete with same binding site as paclitaxel on

-tubulin– Binding mode different from above– Accumulate in G2/M

• Induces conformational changes in Bax (pro-apoptotic protein)

• Bcl-2-dependent• Potential for synergism with Bcl-2 inhibitors

Pharmacologic considerations

• Epothilone A and B– High in vitro tumor activity– Modest in vivo activity– Metabolic instability– Unfavorable PK– Narrow therapeutic window

• Analogs developed to optimize product

Class-specific advantages

• Low susceptibility to tumor resistance mechanisms– MRP-1 and P-gp efflux pumps– (III) tubulin overexpression– -tubulin mutations

Summary of phase II trials of ixabepilone in metastatic breast

cancer

0Roché1

After adjuvant anthracycline

Low2

Taxane-pretreated MBC

Thomas3

Taxane-resistant MBC

Perez4

Anthracycline-, taxane-, and capecitabine-

resistant

Bunnell5

Multiresistant MBC w/capecitabine

42

22

12

30

18a

5

10

15

20

25

30

35

40

45

Overa

ll R

esp

on

se R

ate

(%)

1. Roché H, et al. J Clin Oncol. 2007;25:3415. 2. Low JA, et al. J Clin Oncol. 2005;23:2726. 3. Thomas E, et al. J Clin Oncol. 2007;25:3399. 4. Perez EA, et al. J Clin Oncol. 2007;25:3407. 5. Bunnell CA, et al. J Clin Oncol. 2006;24:Abstract 10511. Graphic courtesy of Hope S. Rugo, MD.

12b

aInvestigator assessed; bIndependent assessed.

0

20

40

60

80

100

BMS 009NCI 0229BMS 010BMS 081BMS 031

Diarrhea at 1 to 11%

Grade 3/4 neutropenia 35 to 58%

Febrile neutropenia 3-14% with 14 % on NCI0229

Sensory neuropathy ranged from 3-22%

Severe myalgias range from 3-26%

Fatigue variable at 6 to 34%

Ixabepilone phase II trialsGrade 3/4 toxicity in metastatic breast

cancer

1. Thomas E, et al. J Clin Oncol. 2007;25:3399. 2. Low JA, et al. J Clin Oncol. 2005;23:2726. 3. Roché H, et al. J Clin Oncol. 2007;25:3415. 4. Perez EA, et al. J Clin Oncol. 2007;25:3407. 5. Bunnell CA, et al. J Clin Oncol. 2006;24:Abstract 10511.

IxabepilonePhase III data

FDA approved ixabepilone in October 2007 as a single agent for triple-resistant metastatic

breast cancer, and in combination with capecitabine

for anthracycline- and taxane-resistant diseaseEMEA CHMP gave a negative opinion and did not recommend a marketing authorization for

ixabepilone for the treatment of locally advanced breast cancer (November 20, 2008)

BMS Pharma EEIG withdrawn its marketing authorization application for ixabepilone

(March 18, 2009)

What were the main concerns of the CHMP?

• The CHMP was concerned that ixabepilone’s benefits in terms of increasing the time until the cancer got worse did not outweigh the concerns over the medicine’s safety.

• In particular, the Committee was concerned over the risk of patients developing neuropathy (damage to nerve cells), which was a severe and common side effect in patients taking the medicine.

• Therefore, at the time of the withdrawal, the CHMP’s view was that the benefits of ixabepilone in the treatment of breast cancer did not outweigh the identified risks.

Ixabepilone(40 mg/m2 IV over 3 hr d1 q3wk)

+Capecitabine

(2000 mg/m2/day PO 2 divided doses d1-d14 q3wk)

N = 375

Capecitabine(2500 mg/m2/day PO 2 divided doses

d1-d14 q3wk)N = 377

Metastatic or locally advanced breast cancer

RESISTANT to anthracyclines

and taxanesN = 752

Stratification •Visceral metastases•Prior chemotherapy for MBC

Study Design: International, Randomized,

Open-label, Phase III Trial

•Anthracycline resistance•Study site

Resistance to Prior TherapyStrict definition: patients whose tumors rapidly progressed in the adjuvant

or metastatic setting after receiving both anthracyclines and taxanes

Setting Anthracycline Taxane

Metastatic ≤3 months of last dose≤4 months of last

dose

Neo/adjuvant

≤6 months of last dose≤12 months of last

dose

Any

Minimum cumulative dose

Doxorubicin: 240 mg/m2

Epirubicin: 360 mg/m2

Median 95% CI

Ixabepilone + Capecitabine

5.8 mo (5.5–7.0)

Capecitabine 4.2 mo (3.8–4.5)

Progression-free Survival by Independent Radiologic Review

P=0.0003

HR: 0.75 (0.64–0.88)

Pro

port

ion

Pro

gre

ssio

n F

ree 1.0

0.8

0.6

0.4

0.2

00 4 8 12 16 20 24 28 32 36

Months

Response Rate

% Response

Investigator IRR

Ixabepilone +

Capecitabine N=375

Capecitabine

N=377

Ixabepilone +

Capecitabine N=375

Capecitabine

N=377

ORR (CR + PR) 42 23 35 14

P<0.0001 P<0.0001

Stable disease 36 38 41 46

Progressive disease

14 29 15 27

Unable to determine

8 10 9 12

.001

.011

<.0001

.005

<.0001

P Value

5

8

68

10

57

<1Febrile neutropenia

4Thrombocytopenia

11Neutropenia

4.5Anemia

6Leukopenia

CapecitabineN = 368

Ixabepilone + Capecitabine

N = 369Toxicity (%)a

aBy worst CTCAE v3 grade.

Grade 3/4 Hematologic Toxicities

Thomas E, et al. J Clin Oncol. 2007;25:5210.

Peri

phera

Peri

phera

l l neuro

pat

neuro

pat

hyhy

23

0

Mya

lgi

Mya

lgi

aa8

0.3

Han

d-

Han

d-

foot

foot

syndro

m

syndro

mee

18 17

Dia

rrhe

Dia

rrhe

aa

69

Muco

siti

Muco

siti

ss

2 2

Vom

itin

Vom

itin

gg

4 2

Fati

gu

Fati

gu

ee

9

3

Nau

sea

Nau

sea

3 2

Art

hra

lgi

Art

hra

lgi

aa

30

0

% P

ati

en

ts

Ixabepilone + capecitabine (n = 369)

Capecitabine (n = 368)

20

40

60

80

Grade 3/4 Nonhematologic toxicities

Thomas E, et al. J Clin Oncol. 2007;25:5210

• Ixabepilone for metastatic breast cancer is an example of a cancer drug that adds "a small benefit at a high cost“

• This editorial accompanies a new cost-efficacy study in the same issue of the journal that found that the addition of ixabepilone to capecitabine adds about $31,000 to the overall medical costs of metastatic breast cancer while providing about 1 more month of "quality-adjusted" survival (Reed et al., 2009).

AgentEpothilone

AnalogClinical Toxicities

Current Development

Phase

Patupilone (EPO906)

Epothilone B Diarrheaa, fatigue, nausea, vomiting III

(ovarian cancer)

II

(ongoing in mBC)

BMS-310705 Epothilone B Hypersensitivity reaction,pancytopenia, neuropathy, arthralgia/myalgia, asthenia, diarrheaa, ataxia, neutropeniaa, hyponatremiaa, vomitinga

I/II

(OR observed in mBC)

Sagopilone (ZK-EPO)

Epothilone B Neuropathya, nausea, ataxiaa II

(ongoing in mBC)

KOS-862 Epothilone D Fatigue, nausea/vomiting, neuropathy, impaired gaita, cognitive/perceptual abnormalitiesa, chest paina

II

(14% PR in A&T resistant mBC)

Drug development discontinued

Dehydelone (KOS-1584)

Epothilone D I

(ongoing)

Epothilones in clinical development

a, dose limiting toxicity; mBC, metastatic breast cancer; A&T, anthracycline & taxane