Making of an antibioticPre Clinical Journey

Dr. Ashok Rattan

Chief Executive,

Fortis Clinical Research Ltd.,

Adviser,

Religare SRL Diagnostics in Fortis / Escorts Hospitals,

Delhi & NCR

We are overwhelmed as it is, with an infinite abundance of vaunted

medicaments; and here they add a new one…..

Thomas Sydenham, MD

(1624 - 1689)

Do we really need new anti- infectives ?

• > 80 efficacious agents available to treat ALL bacterial ; most fungal infections & some viral infections

but

• limitation of spectrum of available drugs

• PK drawbacks: either oral or IV

• Toxicity: acute or sub-acute

• Rapid development of drug resistance

Yes,

Drugs are required to meet

the unmet medical need

New Drug Discovery and Development(Timelines)

DIS

CO

VE

RY

/SC

RE

EN

ING

SYNTHESIS AND PURIFICATION

ANIMAL TESTING

PHASE II

PHASE I

SHORT-TERM

PHASE III

LONG-TERM

PHASE IV

ADVERSEREACTION

SURVEILLANCEPRODUCT DEFECT

REPORTING

PRE-CLINICALRESEARCH CLINICAL STUDIES NDA REVIEW POST-MARKETING

24 + 18 months. AVG: 5 YEARS AVG: 12 MOS.

IND NDA APPROVAL

5000 compounds evaluated

Phase-I

20-100 healthy volunteers

0 2 4 6 8 10 12 1614

Years

Phase-II100-500 patient volunteers

Phase-III

1000-5000 patient volunteers

Review and approval byFood & Drug Administration

1Compoundapproved

5 INDs

Discovery and preclinical testing

Source: Tufts Centre For Study Of Drug Development in C&EN, June 2000

Bringing a new drug to the market can take 15 years

Cost of bringing a new drug to the market is 800M to 1B US$

NCE In vitro In vitro

Acute tox

DRUG

Insoluble

New Drug Discovery is like snakes and ladderfailure is the norm

Active

UnderstandDisease & Identify

unmet needs

SelectMechanism/

Target

DesignNCEs &Screens

Virtual Screening

Synthesize NCEs

ConvertLead-to-IND

Candidate

New Drug Discovery Road MapPreclinical work-up

IND directed regulatory studies

ConvertHit-to-Lead

Screen/Identify Hit

Attributes of a successful target

• Provide adequate selectivity & spectrum

• Essential for growth or virulence

• HTS assay development should be possible

Microarray chip

Image from Gene-Chips (Microarray)

TARGET IDENTIFICATION

& VALIDATION

R&D Technology

HIT IDENTIFICATION LEAD SEARCH

& OPTIMIZATION

CANDIDATE SELECTION GLP PHASE

PHASE I-II PHASE II - III

EXPLORATORY RESEARCH

DRUG DISCOVERY

DRUG PROFILING PRE- DEVELOPMENT

DEVELOPMENT

GENOMICS

PROTEOMICS

PHARMACOGENETICS

BIOINFORMATICS

HTS

ASSAY DEVELOPMENT

SUBSTANCE LIBRARY

MOLECULAR MODELING

COMBINATORIAL CHEMISTRY

IN VITRO &

ANIMAL PHARMACOLOGY

TOXICOLOGY

NEW FORMULATION

PILOT PLANT

PHARMACOGENETICS

DATA MINING

DATA BASE

Next advance will be availability of complete genomic sequences from multiple strains of a single pathogen.

Genomic sequence information

• Selectivity

• Spectrum

• Functionality

• Essentiality

Pre clinical studiesBroad Aim

• Efficacy: in vitro and in vivo

• Safety in animals

Pre clinical studiesObjectives

• To demonstrate anti infective activity against target pathogens

• To examine culture conditions that may modify activity• To determine interaction with other drugs• To provide information of mechanism and potential for

resistance development• To determine therapeutic index• To suggest dose and surrogate markers of efficacy in man

Pre clinical studieswhat needs to be done

• In vitro activity against target and other pathogens

• In vivo efficacy

• Acute and sub-acute toxicity in 2 species

• Genotoxicity

• PK and TK analysis

• Formulation and stability

• Synthesis of NCE under GMP conditions

Efficacy studies

In vitro tests

• Antimicrobial spectrum of activity• MIC 50, MIC 90, G.M.

• Kinetic kill of bacteria

• Cidal or static

• Effect of medium, pH, inoculum, serum

• Interaction with other antibiotics

• Frequency and selection of resistance

• Mechanism of action

30S subunit

50S subunit

AUGCCGGGUUACUAA5’ 3’

mRNA

IFs AUGCCGGGUUACUAA5’ 3’

30S + mRNA fMet-tRNA

AUGCCGGGUUACUAA5’ 3’

70S Initiation Complex

EFs

Elongation factors + t-RNAs

Elongation

Peptide product

Tetracyclines

Macrolides, Streptogramins

Protein BiosynthesisProtein Biosynthesis

Rifampicin, Aminoglycosides

RBx7644RBx7644

30S subunit

50S subunit

AUGCCGGGUUACUAA5’ 3’

mRNA

IFs AUGCCGGGUUACUAA5’ 3’

30S + mRNA fMet-tRNA

Initiation Complex Initiation Complex not formednot formed

Site of action of RBx 7644Site of action of RBx 7644

Protein synthesis inhibition at a novel site

In vivo evaluation

• Objective: – To yield information on the NCE’s biological

activity against representative microbes– PK/PD characteristics– Toxicity

In vivo efficacy models

• Screening

• Monoparametric

• Ex vivo

• Discriminatory

In vitro - In vivo correlation of antimicrobial activity

In vitro In vivo Frequency (%)

- - 45.3

- + 0.3

+ - 39.6

+ + 14.8

54.4 15.1

Reasons for in vivo inactivity of in vitro active compounds

• Microbiological:– Metabolic state of bacteria (dormant bacteria)

– Presence of nonpathogenic inactivating bacteria

• PK– Poor oral absorption or rapid excretion

– Rapid metabolism

– Inability to reach target site - CSF, intracellular

• Biological:– Antagonistic environment - pH

• Toxicity:– Effective dose cannot be given

Drug ability features

• Lipinski’s rule of 5– Poor absorption or permeation more likely if

• More than 5 H bond donors• Mol Wt more than 500• cLog P more than 5• Sum of N and O more than 10

• Physo-chemical property– Solubility, stability

• In vitro ADME Tox screen– Permeability, cell based toxicity, cyp 450 inhibition or

induction, hERG potential, Plasma Protein Binding

SAR

Regulatory studies

Investigational New Drug (IND) application

• Toxicity studies in animals: Acute and sub-acute toxicity studies, in rodents & non-rodents and Ames mutagenicity, should be given in a tabular form indicating species….

(This should be given in Appendix III as per Appendices III and IV of Schedule Y)

Schedule YDrugs and Cosmetics Act

• Animal toxicology:– 3.1 Acute Toxicology : at least 2 species– 3.2 Long term toxicity : 2 mammalian species, of

which one should be a non rodent– 3.3 Reproduction studies– 3.4 Local toxicity– 3.5 Mutagenicity and Carcinogenicity

• Animal pharmacology– Dose response, ED50

Yes,

Drugs are required to meet

the unmet medical need