1. Antibody and prodrug therapy of cancer
Steve Roffler
Institute of Biomedical Sciences
Academia Sinica

2. Overview Cancer drug therapeutic index
Antibody targeted prodrug activation
9ACG - new glucuronide prodrug
Surface expression of proteins
scFv activation of T cells
Membrane suicide gene therapy

3. Effective medicines require a therapeutic index > 1
Toxic drug concentration
Therapeutic concentration
Property of tumor cells
Unique or over-expressed target in cancer cells
Relative resistance of normal cells
Tumor targeting

4. Alkylating agents kill dividing cells

5. Basis for cancer drug therapeutic index
Property of tumor cells
Unique or over-expressed target in cancer cells
Relative resistance of normal cells
Tumor targeting

6. Nature Reviews Drug Discovery 1: 493-502, 2002
Gleevec
Nature Reviews Drug Discovery 1: , 2002

7. Topoisomerase I inhibitors

8. Basis for cancer drug therapeutic index
Property of tumor cells
Unique or over-expressed target in cancer cells
Relative resistance of normal cells
Tumor targeting

9. Cyclophosphamide metabolism

10. Basis for cancer drug therapeutic index
Property of tumor cells
Unique or over-expressed target in cancer cells
Relative resistance of normal cells
Tumor targeting

11. Antibody-targeted cancer therapy
Nature Cancer Reviews 1: , 2001

12. Nature Cancer Reviews 1: 118-129, 2001

13. Antibody-directed enzyme prodrug therapy
∆ Flexibility
∆ Amplification step
∆ Bystander killing

14. ADEPT

15. Summary of previous findings
BHAMG times less toxic than pHAM in vitro
Mechanism of low prodrug toxicity
Produces strong bystander effect in vitro and in vivo
Clearance of immunoenzyme improves tumor localization
Cured rat hepatocellular carcinoma tumors

16. Immunoenzymes for human cancer therapy
+ mAb B72.3 against TAG-72
+ on colon, breast, ovarian, lung cancers
+ employed for imaging in over 1000 patients
+ TAG-72 in not internalized

17. Immunoenzyme localization

18. ADEPT therapy of human colon xenografts

19. ADEPT therapy of rat malignant ascites
Day 0 Inject 1.5x107 ADS-30D cells
Day 1 Inject 1.5x107 AS-30D cells
Day 7 Inject RH1-bG immunoenzyme
Inject BHAMG prodrug

20. In vivo depletion of immune cells during ADEPT

21. T cells are important for control of metastasis during ADEPT

22. Glucuronide prodrug of camptothecin
- poor water solubility
- converted to inactive form in vivo
- high toxicity

23. 9ACG 9-aminocamptothecin glucuronide

24. Properties of 9ACG - 100 to 2000 times more soluble than 9AC
- stable in human serum for >72 h
Km = 31.0 µM
Vmax = 10.9 µmole/µg-min

26. 9ACG activity against human lung cancer

27. Low dose 9ACG vs. topotecan

28. Mechanism of 9ACG activation
9ACG activated by ß-glucuronidase at tumor?
Source of ß-glucuronidase - tumor or immune cells?
anti-mouse ß-glucuronidase
anti-human ß-glucuronidase
ß-glucuronidase KO tumor
ß-glucuronidase KO mice