Pre-Clinical Studies and Pharmacology of 13-Cis-Retinoic Acid in Neuroblastoma

C. Patrick Reynolds, MD PhD

Childrens Hospital Los Angeles

University of Southern California

Children’s Oncology Group

Control 10 M Retinoic Acid

High-Dose, Pulse Retinoic Acid Induces Neuroblastoma Differentiation

Regulation of Transcription by Retinoids

Transcriptional Repression

RARE

ATRA

RAR

CPB/p300

9-cis-RAACTR

Activation of

Transcription

RXR

AGGTCA 5bp AGGTCA

RARE

RXR RAR

SMRTor

N-coR

mSin3a

HDAC1

AGGTCA 5bp AGGTCA

Naturally Occurring Retinoids

all trans-retinoic acid

retinol (vitamin A)retinal

9-cis-retinoic acid

13-cis-retinoic acid

10 M Retinoic AcidControl

Retinoic Acid Induces Prolonged Differentiation and Growth Arrest in SMS-LHN

Day 28 (RA for 14 days, control passed x 4)

13-cis-Retinoic Acid Causes Sustained Growth Arrest of Neuroblastoma

• Neuroblastoma cell line given two pulses (2 weeks each) of 5 M 13-cis-retinoic acid

• MYCN protein expression by immunoblotting was down-regulated

• Phase I study achieved levels of 7.2 + 5.3 M peak and 4.1 + 2.7 M trough

DAYS

0 14 28 42 56 70 84 98 112126

% C

ON

TR

OL

0

20

40

60

80

100

RA RA

0 14 28 42 56 70 84 98 112126

CE

LL

NU

MB

ER

103

104

105

106

107

108

109

1010

Control

13-cis-RA

13-cis-RA

MYCN Expression

Pharmacokinetics of 13-cis-Retinoic Acid

Pharmacokinetics of 13-cis-Retinoic Acid

13-cis-RA Shows Stable AUC During Therapy

Formulation Sub-Optimal For Young Children • Liquid in soft gelatin capsule (10, 20, 30, 40 mg)

• Can be pierced and chewed or children trained to swallow

• Often must be squeezed into food for young children causing increased dosing variability

• Out-of-capsule administration may be associated with decreased 13-cis-RA levels Veal et al, Br J Cancer 96:424, 2007

• Extemporaneous liquid formulations have been associated with toxicity likely due to metabolism to ATRA

Drug Antagonism by 13-cis-RA in Neuroblastoma

SMS-KCNR

SMS-SAN

High-Risk Neuroblastoma Burden During Therapy

13-cis-RA ?LONG-TERM SURVIVAL

How can 13-cis-RA For Neuroblastoma Be Improved ?

• Isotretinoin labeling should include recommended dosing and approaches to use of the existing formulation in pediatric oncology

• Pharmacokinetic and possibly pharmacogenomic studies could allow for PK and/or PG-guided dosing

• Further study on administration route (in or out of capsule) effects on PK are needed

• A stable formulation suitable for young children and safe for handling by women of child-bearing potential would be optimal

Acknowledgements

Clinical Trials

Judy VillablancaKate MatthayBob SeegerChildren’s Oncology Group

Pharmacokinetics

Vas AvramisAnis Khan

The Patients and Parents who Participated in our Clinical Trials