Post on 10-Jul-2015
transcript
GE-511
PRESENTED BY
GANDRATHI KULDEEP KUMAR
M.S.(PHARM), I SEMESTER
DEPARTMENT OF PHARMACEUTICS
NATIONAL INSTITUTE OF PHARMACEUTICAL EDUCATION AND RESEARCH
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Introduction
Antibody-Directed Enzyme-Prodrug Therapy
Advances in ADEPT
Conclusion
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Many therapies are used for the treatment of cancer
These therapies suffer from many limitations
Limitation to the on-going treatments is due to
Drug resistance
Lack of selectivity
Pathway redundancy
Many chemotherapeutic agents-narrow therapeutic index
A more efficient approach is needed
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It was proposed by Dr. Bagshawe et al
Advantageous over conventional therapies
Involves 2 steps:
Administration and localization of antibody-enzyme complex in tumor cell
Selective conversion of prodrug by antibody-enzyme fusion protein
4Afshar, S et al., Molecular cancer therapeutics 8, 185.
TUMOR CELL
Mechanism of ADEPT
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Bagshawe, K.D et al., 1999. Current opinion in immunology 11, 579-583.
Better understanding of the therapy
Identification of antigen
Penetration of antibody-enzyme fusion protein
Elimination of biological molecules might be
non-linear
Enzyme specific prodrug activation
7Fang et al., 2008. Drug Metabolism and Disposition 36, 1153-1165.
Use of different
enzymes in
ADEPT
Modifications in
antibody-enzyme
complexes
Phase-I clinical
studies
Optimization of
ADEPT- mathematical
models
ADVANCEMENTS IN ADEPT
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Enzymes
employed
in ADEPT
Non-human
enzymes
Intracellular
human
enzymes
Engineered
human
enzymes
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Vast number of prodrugs can be designed
Bacterial enzymes are generally employed
Many studies were reported on bacterial carboxypeptidase G2
Limited by their immunogenecity
Modified, in the recent times, to reduce immunogenecity
Example: Reduction in immunogenecity of β-lactamase
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Contd...
Non-human enzymes are more efficient compared to human enzymes
Example:
Activation of prodrug CPT-11 to the active drug SN-38 is very fast using rabbit carboxylesterasescompared to the human enzymes
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These are produced by inducing mutations in human enzymes
Less immunogenic compared to non human enzymes
Substrate specificity of wild type enzymes is altered
Example:
Double mutant (hDM) of human Poly Nucleoside Phosphorylase (hPNP)
Afshar, S et al., Molecular cancer therapeutics 8, 185.
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They are present only within the cell
No systemic activation of prodrugs will be observed
Recent strategy employed in ADEPT
Less immunogenic compared to non human enzymes and engineered human enzymes
Example: Post Proline cleaving endopeptidase
N-Protected glycine-proline
dipeptidedoxorubicin
Doxorubicin
Heinis, C et al., 2004. Biochemistry 43, 6293-6303.
S.No Enzyme Prodrug Drug
1 DT diaphorase 5-(Aziridin-1-yl)-2,4-
nitrobenzamide (CB 1954)
5-(Aziridin-1-yl)-4-
hydroxyl amino-2-
nitrobenzamide.
2 Plasmin Peptidyl-p-phenylene diamine-
mustard
Phenylenediamine-
mustard
3 Carboxypeptidase G2 Benzoic acid mustard
glutamates
Benzoic acid
mustards (various)
4 Thymidine kinase (viral) Ganciclovir* Ganciclovir
triphosphate
5 Cytosine deaminase 5-Fluorocytosine* 5-Fluorouracil
6 β –Glucosidase Amygdalin Cyanide
7 β –Lactamase Nitrogen-mustard-
cephalosporin
Nitrogen mustards
(various)
8 Alkaline phosphatase Phenol mustard phosphatase*
Doxorubicin phosphatase*
Phenol mustard
Doxorubicin
9 Cytochrome P-450 Cyclophosphamide
Ifosfamide
Phosphoamide
mustard
(+ acrolein)
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Enzymes and prodrugs proposed for cancer therapy
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Use of humanized antibodies and enzymes
Example: humanized disulfide-stabilized anti
p185HER2 Fv-β-lactamase fusion protein
Accelerated clearance of Ab-E fusion protein
Usage of clearance antibody
Hypermannosylation of recombinant antibody-enzyme fusion protein
Rodrigues et al., 1995. Cancer Res 55, 63-70.
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Produced via post translational modifications in
Pichia pastoris
Elimination is well understood
Complex eliminates via mannose receptors
Macrophages (spleen) and endothelial cells (liver) are
mainly responsible for the elimination of complex
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With A5CP conjugate and CMDA prodrug
It required additional clearance antibody
100% patients developed HAMA and 97% HACA
With recombinant MFECP1 and Bis-iodo phenol
prodrug
Only 31 patients were taken
36% patients developed HACA and none of them developed HAMA
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Treatment with MFECP1
(units/m2) and BIP prodrug
(mg/m2 X3)
No. of patients Toxicity
5000 MFECP1 + 12.42 BIP
prodrug
Plasma CPG2
0.0111units/mL (median)
3 G3 thrombocytopenia (1), G3
neutropenia (1), G3 leukopenia (1)
5000 MFECP1 + 1075 BIP
prodrug
Plasma CPG2
<0.002units/mL
1 G4 ALT/AST, G3 GGT, G4 Cr/urea,
G3 anemia, G3 leukopenia, G3
thrombocytopenia
3000 MFECP1 + 537.6 BIP
prodrug
Plasma CPG2
<0.002units/mL
2 G4 ALT/AST (1), G3 anemia (1), G3
thrombocytopenia (1), G3
leukopenia (1), G3 fatigue
1500 MFECP1 +200 BIP
prodrug
1 G3 thrombocytopenia (1)
Abbrevations: G3 :Grade 3, G4: Grade 4, ALT: Alanine aminotransferase, AST: Aspartate aminotransferase
GGT: ϒ-glutamyl transferase
Dose escalation and toxicity of BIP prodrug
Mayer, A. et al., 2006. Clinical cancer research 12, 6509-6516.
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To predict therapeutic outcome before preclinical
and clinical studies
Two models were applied:
Compartmental model: Failed to describe pharmacokinetic
properties of biological molecules
Physiology based Pharmacokinetic (PBPK) model: Applied to
analyse each compartment or organ.
Galluppi et al., 2001. Clinical pharmacology and therapeutics 69, 387.
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For an effective ADEPT
Optimal clearance of Ab-E is 1.5X10-3 ml/min
Optimal Emax of Ab-E for prodrug conversion is 600 min-1
Optimal Permeability of prodrug is 1.4 X 10-4 cm/sec
Optimal dosing interval of Ab-E and prodrug is 5 days
Galluppi et al., 2001. Clinical pharmacology and therapeutics 69, 387.
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ADEPT was proved to be a potential therapy for the
treatment of cancer. Clinical trials of ADEPT proved
this fact but the therapy is limited by toxic effects,
many of which were being addressed in the recent
years
Further research has to be encouraged in the future
as ADEPT has the potential of being the successful
therapy in the treatment of cancer in the future
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