Crystallography as a Drug Design and Delivery Tool · 2016-08-17 · Drug Design Using Structural...

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“Crystallography as a Drug Design and Delivery Tool”

The 2016 DDDS is co-produced with ACS Division of Medicinal Chemistry and the AAPS

Vincent Stoll Research Fellow and Associate

Director of Structural Biology, AbbVie

Robert Wenslow Vice President, Business

Development, Crystal Pharmatech

Andrew Brunskill Associate Principal Scientist,

Merck

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Drug Design Using Structural Biology

Vincent S. Stoll, Ph.D. Associate Director Structural Biology R&D, AbbVie

No Pro Approval Code A4360572

Protein Biochemistry Molecular Biology

The Drug Design Cycle

Iterative structure-based drug design cycle

3D Structure Determination Crystallography/NMR Homology Modeling

Structure-based Drug Design Cycle Analog Design

Lead Generation

Chemical Synthesis

Biological Assays

Medicinal Chemistry-based Cycle

Preclinical Studies

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Protein Production – Protein Biochemistry Protein production pathway – an iterative process

Project team Chemists Biologists

Purification Characterization

Fermentation Cloning and expression

Crystallography NMR

Production Customers Beneficiaries .

Cycle to improve expression, solubility, activity, stability

Cycle to improve crystallizability,

spectral quality, etc.


How Do We Determine the Crystal Structure?

Solution of target protein

Crystal of protein in

drop

Add precipitant


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drop

Add precipitant


Soak ligand into crystal




drop

Add precipitant

Ligand soaks in over 2-24 hours

X-ray Generator

Crystal mounted at liquid nitrogen temperature

(–196 °C)


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Protein Crystal X-ray Diffraction

mounted crystal

X-ray beam

Intensities transformed to electron density

Scatters X-rays in discrete directions (image 0.2° wedge of 180° crystal rotation scan)

3D atomic model

Integrate with AbbVie Projects

Single wavelength (~0.1 nm) Single crystal (10~100 µm)


22 SBBD| Drew Medicinal Chemistry Course| 6.8.16

Global X-ray Crystallography

Using State of the Art Technologies • Highly automated crystallization process

– UV Florescence and Absorbance crystal viewing

– Lipidic cubic phase dispenser – Micro crystal mounting system

– Currently manual, automation in development

– Image viewing software – Novel approach to compound solubility

measurement (Critical Aggregation Concentration) – Helps characterize and prioritize

compounds for crystallization

• Commercially purchased automation – Mosquito for nanoliter solution dispensing

• Protein supplied by centralized Protein Biochemistry

Driving FBDD & SBDD on small Molecules and Biologics

Crystallization Screening

Crystallization Optimization

Crystal Plate Viewing Tower

Crystal Identification

Microcrystal Scooping

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Enabling Challenging Experiments

• Diffraction Rastering sample centering • Collect-Along-Vector

• Mini-Beam 50, 20, 10, 5 m

• Stable Beam auto positional feedback

• High-Precision Alio Goniometer reliable sample positioning

• High Flux >1013 ph/s @ 12.4 keV

• Micro-Focused Beam 30 m(v) x 70 m(h) FWHM

• Fast Detector Pilatus 6M, no readout noise

Weakly Diffracting

Crystals

Small Crystals

Lipidic Cubic Phase

Crystals

Radiation SensitiveC

rystals


Crystallography Experiments @ IMCA-CAT


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20,000+ structures annually

INDUSTRY DISCOVER CAPABILITIES PRODUCTIVITY EXPERIMENT

IMCA-CAT Subscribers

New subscriptions available

IMCA Members

www.imca-cat.org

• proprietary

• rapid & frequent access

• on-site, remote, mail-in • focused, intense beam

• mini beam 5-50 m

• pucks: Uni, ACTOR, ALS

• high-throughput

• fast, encrypted data transfer

• real-time integration to company pipelines

Beamline 17-ID @ APS

• micro crystals

• membrane proteins

• MAD / SAD

• in situ

• diffraction rastering

• collect-along-vector

• auto collect & process


Structure-based Drug Design

Bcl Inhibitors, Fragment-based Drug Design, and Anti-targets


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Bcl-2 Family Inhibitor – a Protein-Protein Interaction

• Potential as a therapeutic option in a range of cancers

106 Business Week | December 12, 2005


(ABT-737is an investigational Compound. Safety and Efficacy have not been established)

27

Bcl-2 Family Inhibitor Helps Turns on Death Switch

Bcl-xL

Overproduction of Bcl-2 protein binds to death proteins and shuts off the death switch allowing

cancers to stay alive

Death Protein

In cancer cells

Muchmore et al., Nature 381, 335 (1996) Sattler et al., Science, 275, 983 (1997)

How Bcl-xL binds to death proteins

Bcl-2

like

BH3- only +

Cancer cells live

Bcl-2

like

BH3- only

Bcl-2 family inhibitor

binds to Bcl-2 and helps blocks death protein interaction, allowing death protein to kill cancer

Cancer cells die

BH3- only

Bcl-2

like +

Bcl-2

like


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Bcl-xL Structure of Binding Site

• Goal is to design a compound to mimic Bak peptide binding

• Hydrophobic residues interact with Bcl-xL:

– Leu 78, Ile 85

• Hydrophilic residues point out into solvent:

– Arg 76, Asp 83, Asp 84

• Take advantage of groups to design compound

R139

L78

D83

I85

Bcl-xL complexed to Bak peptide

R76

29

O

O Screen for fragment #2

OH

Screen for fragment #1

1H (ppm)

13C

(p

pm

)

Fragment Screening and Linking – SAR by NMR

NH

N

O

HN

NHN

N

N

N

O

Cl

HN O NH2

CH3

H3CO

CH3

H3C

COOH

10,000 fragment

library


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• Perform 2nd site screen

• Determine ternary structure

• Design linkers and synthesize

• Confirm design with structure

O

O Screen for fragment #2

OH

Screen for fragment #1

Fragment Screening and Linking – SAR by NMR

NH

N

O

HN

NHN

N

N

N

O

Cl

HN O NH2

CH3

H3CO

CH3

H3C

COOH

10,000 fragment

library

Link fragments

O

O

O


Fragment Collection Fragment Screening Fragment Optimization

NMR SPR

Triage

Lead

Ro3 and Ro3.5 Collections

Overall Fragment Screening Paradigm

BP Collection

BP Similars

HTS

BioPhys (BP)

BPS

SBDD

Screening and confirmation

Biochemical assays XRC

Synthesis Screening

Design (XRC and Props)

Purification and sample

logistics


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Screen for First-Site Ligands using NMR

• 10,000 compound library

• <MW> ~ 215

• [Compound] = 1 mM

9.0 8.5 8.0

111

.011

0.0

109

.01

08

.01

07

.01

06

.01

05

.0

1H ppm

15N

ppm

OH

OF

Kd = 300 M

Monitor Binding with 15N-HSQC spectrum

G94 G196

G138


R139

NMR Structure of Bound Fragment

Binds to peptide “hot spot”

• Two key interactions maintained (Leu78 and Asp83)

Second site accessible • Ile85 pocket of Bak peptide


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Screen for Second-Site Ligand

• Screen in excess of biaryl acid

• 3,500 compound library

• <MW> ~ 150

• [Compound] = 5 mM

OH

Kd = 2000 M

• Binds to second “hot spot” ─ Ile of Bak peptide

R139


Linking Strategy

6.1 Å

F97 F

OHO

OH

Kd = 2000 – 6000 M

Kd = 300 M

linker

O

O

O


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Linking Strategy

• Accesses hydrophobic second site

• 200-fold gain in potency

– Expected >150-fold

• Still room for improvement

FPA IC50 = 1.4 µM

F

O OH


Acylsulfonamide Linking Strategy

New trajectory: avoids F97

Maintains acidic nature

Acidic Hydrogen

Kd = 300 µM Kd = 320 µM

R = Me

F

OHO

F

NH

OS

R

O O

O

O

O

F97


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Diversity Approach to 2nd Site Binders

Parallel synthesis

F

O OH

React with 120 diverse

sulfonamides

R-SO2NH2

F

OHN

S

HN

O O

NS

NO2

Kd = 245 nM

React with 125 diverse amines

HNRR'

F

OHN

S

O O

NO2HN

S

Kd = 36 nM

Kd = 300,000 nM

Kd = >10 µM in 10% serum!


Structure-Based Optimization of Bcl-xL Inhibitors

Kd = 36 nM

Structure-based reduction in

protein-binding

Polar isostere for phenyl ring

Accessing a “third” pocket In the groove

Nature 435, 677-681 (2005)

Tail collapses increases potency

F

NH

OS

O O

NH

S

NO2

N

N

NH

OS

O O

NH

S

NO2

H

N

Cl

ABT-737 KD < 1 nM


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ABT-737 – The Clinical Candidate

ABT-737 Clinical candidate

Kd < 1 nM

F

NH

OS

O O

NH

S

NO2

N

N

NH

OS

O O

NH

S

NO2

H

N

Cl

Fits the structure-based design rubric


42

Audience Survey Question ANSWER THE QUESTION ON BLUE SCREEN IN ONE MOMENT

• They identify and bind key hotspots in a binding site.

• Linking two fragments together is easy.

• They often lead to more efficient drugs with better physical properties.

• Fragments are easy to optimize in chemistry without protein structural information.

What are some of the advantages of using fragments in drug discovery?

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ABT-263: Making an Oral Drug

Main liability of ABT-737 is its poor oral bioavailability

• Must be dosed IV

This is due to limited absorption

• Very basic dimethyl amine

• Rigid chloro-biphenyl

Nitro group potentially toxic

N

OS

HN

OO

HN

NO2

S

N

N

Cl

ABT-737 Oral Bioavailability ~ 5 %


N

OS

HN

OO

HN

NO2

S

N

N

Cl


N

OS

HN

OO

HN

NO2

S

N

N

Cl


N

OS

HN

OO

HN

S

S

N

N

Cl

OO

F3C

Remove potential toxicity


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N

OS

HN

OO

HN

NO2

S

N

N

Cl

N

OS

HN

OO

HN

S

S

N

N

Cl

OOO

F3C

Decrease basicity by one log unit





N

OS

HN

OO

HN

NO2

S

N

N

Cl

N

OS

HN

OO

HN

S

S

N

N

Cl

OOO

F3C



Decrease rigidity, improve absorption



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N

OS

HN

OO

HN

NO2

S

N

N

Cl

N

OS

HN

OO

HN

S

S

N

N

Cl

OOO

F3C



Decrease rigidity, improve absorption




ABT-263 – The Current Clinical Candidate

Also fits the structure-based design rubric

ABT-263 Clinical candidate

Kd < 1 nM

N

OS

HN

OO

HN

S

S

N

N

Cl

OOO

F3C

48

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Navitoclax Induces Thrombocytopenia Bcl-xL driven toxicity

• Platelet survival is dependent on Bcl-xL

– Mason, et. al., Cell 128, 1173, (2007).

• Bcl-xL inhibition with navitoclax results in concentration and dose dependent thrombocytopenia

• Thrombocytopenia is the clinical dose limiting toxicity of navitoclax Roberts et al., J Clin Oncol 27:15s, abstr 3505 (2009)

Wilson et al., Lancet Oncol 11, 1149, (2010)

R2 = 0.9466

0

10

20

30

40

50

60

70

80

90

1 10 100 1000

Dose (mg)

% o

f B

as

elin

e P

late

lets

Platelet count vs. drug exposure Platelet count vs. dose %

of

Ba

se

lin

e P

late

lets

AUC0-inf (ug·h/mL)

(Navitoclax is an investigational Compound. Safety and Efficacy have not been established)

49

Bcl-xL

navitoclax

Bcl-2

Dose-limiting

thrombocytopenia

Navitoclax Inhibition Profile Dictates Efficacy/Toxicity

• Bcl-2 is an important survival factor in lymphoid malignancies

– CLL, NHL

• Bcl-xL is required for survival of circulating platelets

– Bcl-xL inhibition leads to dose-limiting thrombocytopenia



Target efficacy in leukemia and lymphoma

50

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Bcl-xL

navitoclax

Bcl-2

Dose-limiting thrombocytopenia

Target efficacy in leukemia and lymphoma

Bcl-2 selective

Bcl-2 Selective Inhibitors: Key Hypotheses

• Bcl-2 selective inhibitors will maintain efficacy in lymphoid malignancies

• Bcl-2 selective (Bcl-xL sparing) inhibitors will not induce thrombocytopenia

• Will result in improved therapeutic window, allowing higher exposures and greater efficacy in Bcl-2 dependent malignancies



51

Bcl-2 & Bcl-xL Binding Grooves Show High Similarity

• No naturally occurring, Bcl-2 selective BH3-only protein

• Only 4 residues differ within binding groove

R126 S122 L108 M112

A104 D108

E96 D100

Bcl-2 Bcl-xL


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N

N

OHN

Cl

SO O

HN

N+O-O

N

S

O

Reverse Engineering Leads to Bcl-2 Selectivity

• Modification of P4 binding region • Loss of Bcl-xL affinity • Reduced Bcl-2 affinity • No cellular potency

N

N

OHN

Cl

SO O

HN

N+O-O

N

O

TR FRET, Ki, [nM]

Bcl-2 Bcl-xL

1 0.20 1.3

2 29 >660

3 18 >660

1 2 3

-P4 binder

-amine N

N

OHN

Cl

SO O

HN

N+O-O

O


Design Cues From X-ray Crystal Artifact

• Overall ligand binding conformation maintained

• P4 pocket occupied by Trp28 in N-terminal loop of neighboring protein in crystal

• Trp side chain forms H-bond with Asp100 of Bcl-2

– Corresponds to Glu96 of Bcl-xL

• Suggests alternate approach to Bcl-2 P4 hot spot

Bcl-2 X-ray

P4

Bcl-2 X-ray

Asp 100

Intercalating Trp

Asp 100


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ASP 100

• ~100-fold increase in Bcl-2 affinity • Selectivity vs. Bcl-xL maintained

• Affinity & cellular efficacy still ~10-fold lower than navitoclax • Target second hydrogen bond and improve cellular activity

Indole Substituent Fills P4 & Captures H-Bond

O

HN

N

N

Cl

NO2

ONH

SOO

ASP 100

TR FRET, Ki, [nM] Bcl-2 Bcl-xL

navitoclax 0.04 0.05

3 18 >660

4 0.30 >660

3 4

2.8

R104

D100

O

O

HN

N

N

Cl

NO2

O

NH

NH

SOO

+ P4 indole


ABT-199: a Selective Bcl-2 Inhibitor

• High Bcl-2 affinity

• Lower affinity for Bcl-xL, Mcl-1

• Ineffective in Bcl-xL-dependent human tumor cell lines (H146)

Affinity Cellular Efficacy, EC50, nM

TR FRET, Ki, nM Human Tumor Cell Lines, 10%HS

Agents Bcl-2 Bcl-xL Bcl-w Mcl-1 RS4;11 (Bcl-2) H146 (Bcl-xL)

navitoclax 0.04 0.05 7 >440 110 75

4 0.30 >660 NT >440 1180 >10,000

ABT-199 < 0.01 48 21 >440 8 3600

4 ABT-199

O

O

HN

N

N

Cl

NO2

O

NH

NH

SOO

O

O

HN

N

N

Cl

NO2

O

N NH

NH

SOO

Souers et al, Nature Medicine 2013 (ABBV-199 is an investigational Compound. Safety

and Efficacy have not been established)

56

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Physicochemical Properties

Property ABT-199

Mol Wt (g/mol) 868.44

cLogP 8.1

PSA 183

Experimental logD 5.4

Aqueous solubility pH 1

25 °C, (g/mL) 2.3 ± 0.2

Aqueous solubility pH 7.4 ,

25 °C, (g/mL), <0.004

• High molecular weight • Hydrophobic

• Low aqueous solubility

O NH

O

HN

N

N

Cl

N NH

N+O–O

SO

O

O


ABT-199 is Orally Bioavailable

• Modest oral bioavailability across species

– Low clearance

– Good plasma half-life

• Amorphous solid dispersion allows high exposures and good dose linearity

PEG400/DMSO i.v. t1/2

(h)

i.v. V

(L/kg)

i.v. CLP

(L/h/kg)

Oral t1/2

(h)

Oral F

(%)

Mouse 2.5 0.38 0.10 2.7 28

Rat* 5.8 2.0 0.24 5.3 29

Dog 12.0 0.3 0.02 13.8 28

Cyno 2.2 0.9 0.27 2.0 9

* PEG400:Cremaphor EL:Oleic Acid

Dog 2.5 mg/kg i.v. or p.o.

ASD formulation Dog AUC vs. p.o. Dose

Dose (mg/kg)

AU

C (

ug

*hr/

mL

)

R 2

= 0.9746

0

500

1000

1500

2000

2500

0 50 100 150 200


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ABT-199 Has Platelet Sparing Potential

• Navitoclax 5 mg/kg po qdx1 results in ~95% platelet loss in dogs within 6 hours

• ABT-199 has minimal platelet effect at ~20-fold higher dose and exposure

• ABT-199 is significantly less potent than navitoclax against human platelets ex vivo (n=9)

dogs in vivo Single oral dose

0.083 M 5.483 M

Human platelets treated ex vivo

100 90 80 70 60 50 40 30 20 10 00 500 1,000 1,500 2,000 2,500

AUC (µgh/ml) Max platelet reduction (%)

ABT-199

navitoclax

vehicle

150 mg/kg

50 mg/kg

25 mg/kg

5 mg/kg

Souers et al, Nature Medicine 2013


(ABBV-199 is an investigational Compound. Safety and Efficacy have not been established)

59

ALL Cells are ‘Primed for Death’ ABT-199 helps induces tumor regressions in preclinical models

0

500

1000

1500

2000

2500

3000

20 25 30 35 40 45 50 55

ABT-199 100 mg/kg PO, qdx7

Vehicle

Tu

mo

r vo

lum

e (

mm

3)

RS4;11 (ALL) flank xenograft In female C.B-17 SCID Mice

Days post-inoculation

• High Bcl-2 & Bim expression

• High levels of Bcl-2:Bim complex

• ABT-199 induces complete regression of established tumors

Tumor Cell Lines

Del Gaizo Moore, et.al. Blood. 111, 2300, (2008)


(ABBV-199 is an investigational Compound. Safety and Efficacy have not been established)

60

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Summation


Conclusions

• Protein-protein interactions can be suitable drug targets

• Structural understanding of the PPI is key

- Know your target: protein hot spots

- Learn from nature: endogenous ligand binding

• Fragment based screening identifies multiple hot spot binders

• Chemical tools are key to understanding biological processes

• Targeting apoptotic machinery may be an effective approach to treat certain cancer types


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Structure-based Drug Design Concepts

• Initial lead-protein complex structures usually provide greatest benefit – Identify ligand binding site and binding mode

– Show critical ligand-protein interactions

– Explain structure-activity relationships

– Suggest positions and groups for modification

• Achieve a consistent binding mode – Allows for reliable prediction

• Develop strategy for modification – Add and combine substituents

– Link fragments

• Focus on all drug properties – Potency, metabolism, solubility, protein binding, pharmacokinetics,

bioavailability


Bcl Project Team

High Throughput Screening

and Fragment Screening

Team

Structural Biology

Acknowledgments

+ many, many others


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Never Give Up!


Crystal Pharmatech

– Your Partner for Pharmaceutical Solid State

Research and Development Solutions

Crystallography as a Drug Design and Delivery Tool:

Robert Wenslow, Ph. D. [email protected]

Crystal Pharmatech

66

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67

• Importance of API Crystals

• Types of Crystals

• Choosing the right Crystal (or lack thereof)

– Salts

– Amorphous

– Co-Crystal

Outline

68

•The most significant challenge facing discovery organizations is understanding reasons why drugs are failing in development.

•A review of Phase II failures (2008-2011) in Nature Reviews Drug Discovery showed that efficacy was the major cause (51%) followed by strategic reasons (29%) and safety (19%).

Why do Compounds Fail

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69

Active Pharmaceutical

Ingredient

API Crystals Chemical purity PSD, SA, morphology, density, etc. Stability (chemical and/or physical) Hygroscopisity, color, caking, etc.

Drug Product Bioavailability Efficacy Safety

Crystallization

Critical Role in Ensuring Drug Product Quality

Cryst. Growth Des., 2015, 15 (12), pp 5645–5647

M3

Molecules, Materials, Medicines

70

Late Stage Polymorph

Change

Hydrate impacts dissolution

Crystal Form leads to new

indication

Extensive

Intellectual Property battles

Salt for consistent

bioavailability and shelf life

Crystal Form Impact on Products

http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=bovW0g7LvJALAM&tbnid=SyzHD0WU9PM8RM:&ved=0CAgQjRwwAA&url=http://www.citifmonline.com/?id=1.1273532&ei=tMGPUYqkF8S30AGL1IDoAQ&psig=AFQjCNEodpMoGoD7J-8zKTtFX37zlzRR_A&ust=1368462132423413

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71

Solid forms include • Polymorphs, hydrates, solvates,

amorphous

• Salts and cocrystals

– Polymorphs, hydrates, solvates and amorphous can exist for each salt/cocrystal

• Amorphous dispersions

– Multiple polymers

and concentrations

Harmon et al. AAPS Newsmagazine, 2009, Sept, 14-20.

Solid Form Diversity

72


• About one third

• About half

• About two thirds

• Almost all

In a 2007 study of over 245 compounds, what percentage had multiple crystal forms (Polymorphs, hydrates, solvates)

Stahly. Crystal Growth & Design. 2007, 7, 1007-1026

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73

BCS Classification

74

Current Reality

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75

Ku, Amer. Pharm. Rev. 2010, 13, 22-30

Items Sulfate Form A

p-Tosylate Form A

Stiochiometry Molar

Ratio(API/Acid) 1:1 (IC) 1:1 (NMR)

Counter ion Safety

Safety Class I II

Solid Characterization

Crystal Form Anhydrate Anhydrate

Crystallinity Crystalline Crystalline

Hygroscopicity Slightly

hygroscopic Slightly

hygroscopic

Purity (% Area) 99.1% 98.4%

Solubility

FaSSIF (4 hr) (mg/mL)

2.9 2.0

SGF (1 hr) (mg/mL)

25.5 21.8

Stability Bulk, 80oC, 39h

Physically stable

Chemically stable

Physically unstable

Chemically stable

Recommendation

Sulfate Form A is recommended for further

evaluation

Salts

When Salts Properties

76


• About one third

• About half

• About two thirds

• Almost all

What percentage of drugs are marketed as salts?

P H Stahl and C G Wermuth, Handbook of Pharmaceutical Salts, Wiley VCH, 2002 L. Kumar, A. Amin & A.K. Bansal; Pharm. Technol., March 2008

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• HIV protease inhibitor (MK-693, L-735,524)

• Marketed as CrixivanTM

– Approved 1996

• Low aqueous solubility (< 0.02 mg/mL), pH dependant

• Free base monohydrate first form investigated

Lin et al. The Story of Crixivan Chapter 11 in Integration of Pharmaceutical Discovery and Development: Case Studies, edited by Borchardt et al, Plenum Press, New York, 1998, p 233-255

77

Crixivan

• Initial animal studies used 0.5% methocel and citric acid solutions

– Showed relatively low and variable oral bioavailability with methocel

– Higher and more reproducible results with acid solutions

– Acid solutions were not stable; same degradation seen with solid free form

• Needed a soluble salt

– pKa 3.68, 6.00

Lin et al. The Story of Crixivan Chapter 11 in Integration of Pharmaceutical Discovery and Development: Case Studies, edited by 3- Borchardt et al, Plenum Press, New York, 1998, p 233-255

78

Crixivan

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• Crystalline sulfate salt found

– Ethanolate

– Highly soluble (500 mg/mL)

– Excellent absorption in rats and dogs

– Very hygroscopic

• Sulfate ethanolate selected for development


79

Crixivan

• Stability issues investigated

– Crystalline sulfate ethanolate compared to amorphous

– Salt exhibited minimal degradation; estimated shelf life of 2 yrs at 25C/33% RH

• Satisfactory chemical stability at low RH


• Handling of bulk and formulated drug product below 30% RH and dessication of final product recommended

80

Crixivan

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Yeh et al. Antimicrob Agents and Chemother 1998, 42, 332-338

• Free base and sulfate salt used in human studies

• Sulfate salt in fasted state or with low fat meal gave highest AUC and Cmax

81

Crixivan

• Summary

– Early salt/form selection simplified development

– Problems with early free base properties solved with sulfate salt

– Early animal and clinical studies showed utility of salt

– Sulfate salt physical properties not ideal, but additional studies provided needed solutions for handling, formulation, packaging

82

Crixivan

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• disintegrants / solubilizers • lipid-based delivery systems

83

• prodrugs

Chemical Modification

• micronized

• nano-particles

Particle-size Reduction

• Polymorphs, amorphous

• co-crystals Form Change

Formulation Systems

Not Just Salts

Amorphous “Structure”

84

Local domains with short-range order (20-25 Å)

Microstructure

Microvoids (defects)

Higher-state energy than crystalline

84

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85 Therapeutic Delivery, February 2015 ,Vol. 6, No. 2 , Pages 247-261

Marketed Amorphous Drugs

10+ marketed amorphous drug products

> 80% with improved bioavailability (Newman A. et al J Pharm Sci. 2012)

Overcome Solubility of late stage polymorph

Dispersion - co-crystal also

works

Amorphous coated pellets

– Co-crystal also works

86

Law et al., J. Pharm. Sci. 93 (2004) 563

Douslin et al. JACS 1946, 68, 173

A higher-energy form that offers enhanced solubility, dissolution rate and oral bioavailability

Kaletra

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87

Solid ccx

Exposure to water/SGF

Meta-stable

Free base

free base

acid

Extraction of co- former from lattice of ccx

time

con

cen

trat

ion

co

nce

ntr

atio

n

time

BA BA

No BA change No BA change

ccx = cocrystal

+

= “parachute” prolongs supersaturation (excipient(s) or crystal form by itself)

Co-crystals – potential mechanism

88


• 1776

• 1942

• 1840

• 1996

What year was the first recorded co-crystal discovered?

Kobell FV, Prakt JF. D-glucose: Sodium chloride monohydrate. Chemie. 1843;28:489

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• Weak base, extremely low aqueous solubility

– ~nanograms / mL RT solubility in water at pH 3 – 8

– 0.6 mg/mL at pH 1.2

• High dose drug, significant first-pass metabolism

• Inconsistent oral bioavailability was a major challenge

• Salt forms were intrinsically acidic and hygroscopic

89

N N ONN

N

O

H3C

CH3

O

O

N

N

N

Cl ClH

Itraconazole

• Co-crystals display improved dissolution compared to the crystalline free base

• Comparable dissolution to the amorphous drug coated on beads – SPORANOX® capsule formulation

90

8x10-4

6

4

2

0

[1] (M

)

4003002001000

Time (min)

Sporanox® beads l-malic acid co-crystal

l-tartaric acid co-crystal succinic acid co-crystal

cis-itraconazole

Remenar et al. JACS, 125, 8456 (2003)

Co-crystal vs. marketed product

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91 ICH Q6A, Federal Register, 2000, 65(251), 83041-83063

Regulatory

IDENTIFY all relevant Crystals (or amorphous) for your compound

92 ICH Q6A, Federal Register, 2000, 65(251), 83041-83063

Regulatory

Understand the IMPACT of all relevant Crystals (or amorphous) for your product

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93

Lessons Learned

Crystals (or lack thereof) have significant impact on product quality and performance

Choosing the right Crystal is not a unit operation Staged decision points

Constant Vigilance

Crystals make your “molecule” a “medicine”

94

Special Thanks!

Ann Newman – Seventh Street Development Group and Crystal Pharmatech

Jun Huang – Crystal Pharmatech

Elizabeth Vadas – InSciTech Inc.

Örn Almarsson – Moderna Therapeutics

Carlos Sanrame – Crystal Pharmatech

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95










Merck

96


http://bit.ly/2016ddds

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Merck

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Crystallography as a Drug Design and Delivery Tool · 2016-08-17 · Drug Design Using Structural...

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