Preliminary phase I results of G3139 (bcl-2 antisense oligonucleotide) therapy in combination with docetaxel in hormone-refractory prostate cancer

Preliminary Phase I Results of G3 I39 @cl-2 Antisense Oligonucleotide) Therapy in Combination With Docetaxel in Hormone-Refractory Prostate Cancer Anthony The

transition

from

androgen-dependent

independent prostate cancer ber of molecular genetic pression

of

the

protein cellular

decreases insults

drogen

withdrawal.

bcl-2

Overexpression

Reduction

of

prostate

and

initiated

in

docetaxel antisense

directed

at bcl-2

expression

(HRPC)

HRPC

therapy can be oligodeoxynucleotide

gene

expression.

28 (suppl Company.

lS):67-70.

efficacy a phase I/II study to

has

examine

enhanced

Copyright

in

preclini-

correlative with

Bcl-2

to such and an-

the antitumor in vivo. Thus,

biologic

patients

whether therapeutic

Semin Oncol WB. Saunders

of

Bcl-2

cancer

markedly increases both in vitro and

pharmacokinetic been

by a numoverex-

the pro-apoptotic response as irradiation, chemotherapy,

hormone-refractory cal models of docetaxel

to androgen-

is accompanied changes, including

gene.

W.

with a (G3 139) 0

2001

by

T IS ESTIMATED that 198,100 new patients in North America will have prostate cancer diagnosed in 2001.1 More than 25% of affected individuals will ultimately develop advanced metastatic disease, and most of these patients will die of hormone-refractory prostate cancer (HRPC).* Surgical or chemical castration remains the most efficacious treatment for disseminated prostate cancer. Castration results in tumor cell apoptosis, tumor regression, a decrease in serum prostatespecific antigen (ISA), and relief of clinical symptoms. Albeit marked, this antitumor response is transient, lasting from 18 to 24 months on average and followed by progression to androgen-independent (AI) growth. An increase in serum PSA level and a recurrence of clinical symptoms, including painful bone metastases, herald AI growth and the clinical syndrome of HRPC. HRPC is associated with brief survival time. Despite improvements in chemotherapeutic options for this form of prostate cancer, treatment remains limited to palliative radiotherapy and palliative chemotherapy. HRPC demonstrates intrinsic resistance to chemotherapeutic agents that are diverse in both structure and mechanism of action. Despite several hundred clinical studies of both experimental and approved chemotherapeutic agents in HRPC, most agents produce minimal or no durable antitumor response.324 Furthermore, the chemotherapy currently approved for this inI

Seminars

in Oncology,

Vol 28, No 4, Suppl I5 (August),

2001:

pp 67-70

Tolcher

dication, mitoxantrone and prednisone, has palliative benefit but no demonstrable survival benefit in randomized studies.Q The transition from androgen-dependent growth to AI growth is accompanied by a number of molecular genetic changes. Evidence suggests that the proto-oncogene b&2 may have a critical role in this transition and in the resistance of HRPC to the effects of hormone withdrawal and chemotherapy?s The bcl-2 proto-oncogene belongs to a family of related genes whose proteins regulate programmed cell death in normal and abnormal cell populations.9 Overexpression of Bcl-2 prevents programmed cell death (also termed apoptosis) from numerous stimuli, including chemotherapy, hormone therapy, and irradiation.1°-13 Partial phosphorylation of bcl-2, in addition to the cytotoxic effects of antimicrotubule polymerization, is one proposed hypothesis for the greater than anticipated antitumor activity of docetaxel in HRPC. Docetaxel, both as a single agent and in combination with estramustine, has demonstrated PSA-based response rates exceeding 60%.14J5 The agent is 10 to 100 times more potent than paclitaxel in phosphorylating bcl-2; this difference may account for the different activities of docetaxel and paclitaxel.i6-is Phosphorylation prevents dimerization of bcl-2 to bax and may shift the equilibrium of antiapoptotic and proapoptotic sig nals in favor of apoptosis. Based on this information, it can be speculated that alterations in the ratio of bcl-2 to bax by either incomplete downregulation or inactivation of bcl-2 may alter the clinical sensitivity of a tumor to chemotherapy. Bcl-2 expression may have a critical role in

From the Institute for Drug Development, Cancer Therapy and Research Center, and the Uniwersity of Texas Health Science Center, Sun Antonio, TX. Address reprint requests to Anthony W. Tolcher, MD, 8122 Datapoint Dr #250, San Antonio, TX 78229. Copyright 0 2001 by W.B. Saunders Company 0093s7754/01/2804-1512$35.00/O doi:10.1053/sonc.2001.26906 67

68

ANTHONY

Day 1

6

8

10

Day 22

Day 27

Docetaxel

W. TOLCHER

Day 29

Docetaxel

1

1

G3139 CM

G3139 CIVI

t ..................................................................++ . ........ ................... * ...,.........................................................................................................................

Course 1

Course 2

T t Baseline biopsy, day 6 biopsy, and mononuclear cell collections for Bcl-2 expression Fig

I.

Treatment

schema

of G3 I39

in combination

mediation of the intrinsic resistance of HRPC to chemotherapy. G3 139 is a phosphorothioate antisense oligodeoxynucleotide directed to the first six codons of the bcl-2 messenger RNA (mRNA). Our previous work showed that G3139 hybridizes to bcl-2 mRNA in a sequence-specific manner, degrades bcl-2 mRNA through RNase H-mediated cleavage, and leads to a reduction in Bcli2 protein expression in the LNCaP human prostate cell line. Down-regulation of Bcl-2 protein in prostate cancer models significantly enhances chemosensitivity to docetaxel both in vitro and in vivo. This enhancement of docetaxel-induced cytotoxicity occurs at therapeutically relevant docetaxel concentrations that are also associated with partial phosphorylation of bcl-2. 19~0These results suggest that bcl-2 down-regulation by G3139 in combination with docetaxel-induced bcl-2 phosphorylation represents a multitargeted approach to reduction of bcl-2-mediated chemoresistance in advanced HRPC. Based on these results, we initiated a phase I/II study of G3139 and docetaxel in patients with HRPC. The objectives of this study are (1) to determine the maximum tolerated dose and recommended dose for G3139 combined with docetaxel administered every 3 weeks; (2) to determine the toxicities of this combination; (3) to determine the pharmacokinetics of G3139 and

with

docetaxel

in HRPC.

CIVI,

continuous

IV infusion.

docetaxel; (4) to characterize the biomarkers that may be predictive for bcl-2 down-regulation, induction of apoptosis, and responsiveness to G3139 and docetaxel; and (5) to determine preliminary antitumor activity of the combination. PATIENTS

AND

METHODS

Eligibility Criteria Patients were required to have progressive HRPC, defined as increases in PSA levels on two occasions not less than 2 weeks apart. Patients also must have had evidence of metastatic disease and not tumor marker-only disease recurrence. All patients must have serum testosterone in the castrate range. Patients could continue to receive luteinizing hormone-releasing hormone agonist therapy but could not have received peripheral antiandrogens (eg, flutamide, nilutamide, or bicalutamide)

G3 I39 Dose Dose Level -I I* 2 3 Abbreviation: *Starting

Docetaxel (vW IV Day 6

No. of Patients

5 5 5

50 60 75

3-6 3-6 3-6

7

75

3-6

hYkg4 CIVI Days

l-5

CIVI, continuous dose level.

IV infusion.

bcl-2

ANTISENSE

OLlGONUCLEOTlDE/DOCETAXEL

IN PROSTATE

CANCER

69

RESULTS T&k No. of patients

2, Patient (treatedlevaluable)

Median

age, yr (range)

Median

ECOG

No. of patients Median

Characteristics 1211 I 65 (49-7 I)

performance

status

treated

prior

no. of prior

with

chemotherapy

(range)

I (O-2) 7

chemotherapy regimens

No. of patients

with

prior

taxane

No. of patients

with

prior

radiotherapy

(range)

I (O-4)

therapy

3 4

for at least 4 weeks before study entry. Prior chemotherapy treatment was acceptable for patient entry; for the phase I portion of the study, prior treatment with a taxane was permissible.

The treatment schedule for G3139 and docetaxel is illustrated in Fig 1. G3 139 was administered as a continuous intravenous (IV) infusion through a central venous access device for 5 days before the administration of docetaxel. The sequence and schedule of G3139 and docetaxel used in this study are based on preclinical experimental data indicating that 5 days’ exposure to G3139 was optimal for maximal Bcl-2 protein down-regulation. Courses were repeated every 21 days. Reevaluation of disease status was performed after every second course for bidimensionally measurable disease, whereas a PSA evaluation was performed before the start of every course. The dose-escalation scheme for the phase I study is shown in Table 1. Biologic correlative and pharmacokinetic studies were performed on days 1 and 6 to assess the pharmacodynamic relationship between G3139 therapy and the molecular genetic targets of therapy. All patients had mononuclear cell collections performed at baseline and after the 5-day G3 139 infusion (Fig I). Mononuclear cells normally express Bcl-2 protein, and these cells were examined for evidence of b&2 down-regulation. In addition, in patients with accessible tissue for biopsy, tissue sampling was performed at baseline and immediately before docetaxel administration to assess Bcl-2 and Bax protein expression. These assays will help define the degree of downregulation of Bcl-2 protein expression and any correlation between down-regulation and antitumor response.

Dose

CONCLUSIONS Bcl-2 protein expression appears to play an important role in mediation of resistance to both hormonal and cytotoxic therapies in the treatment of HRPC. The combination of G3139 and do-

G3 I39

bdWW Docetaxel

I

Twelve patients have been entered, and 11 patients are evaluable for at least one cycle. A total of 45 cycles have been administered with a median of four cycles per patient (range, 1 to 8 cycles per patient). Seven patients received prior chemotherapy, including 3 patients who were refractory to taxanes. The pertinent patient demographics for the initial patients are shown in Table 2. Cure rently, accrual is continuing to the third dose level of 7 mg/kg/d G3139 continuous IV infusion for 5 days followed by docetaxel, 75 mg/m2 IV over 1 hour. Dose-limiting toxicities have been encountered only at the highest dose level in one patient during the first course (grade 4 neutropenia for >5 days) and are summarized in Table 3. Anticipated nonhematologic toxicities, including alopecia (grade l), mild stomatitis (grade l), and fatigue, have been observed. In addition, infections from central venous access devices have been encountered in three patients. PSA responses have been observed in 4 of 8 taxane-naive patients. Steady-state G3 139 plasma concentrations are achieved by day 2 and exceed target plasma concentrations of 5 pg/mL. Early indications are that the pharmacokinetic profile of docetaxel is not substantially altered by the coadministration of G3 139. Moreover, biologic correlative assays to date indicate that decrements in Bcl-2 protein expression in peripheral mononuclear cells occur by day 5, supporting the current schedule of G3139 by 5-day continuous infusion (Fig 2).

No. of (mg/m’)

Grade

Patients

No.

of Courses

4

Neutropenia*

Grade

314

Platelets*

Febrile Neutropenia*

Dose-Limiting Toxicifl

I

5/60

3

9

o/o

o/o

o/o

o/o

2

5175

3

16

212

o/o

O/I

O/l

3

7175

5

20

I13

o/o

o/o

112

*No.

of patients

with

hematologic

toxicity

during

first

course/no.

of patients

with

hematologic

toxicity

during

all courses.

70

ANTHONY

Patient

16,800

W.

TOLCHER

001

iZi Day

1

fS’Day6 12,600 Fig B&2 blood

8,400

2. Down-regulation of expression in peripheral mononuclear cells (MNCs)

on day 6 v day I. Peripheral blood cells were collected on day I, before G3 I39 administration, and day 6, after 5 days of G3 I39 treat-

4,200

ment. MNCs were isolated incubated with fluorescein

0 100

10’

thiocyanate (FITC)-labeled Bcl-2 antibody (Dako, ria, CA) and subjected cytometric evaluation.

IO’

Bcl-2 FITC

cetaxel represents strategy to address resistance and will the emerging role advanced prostate

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