RepliGen is a biopharmaceutical company with late-stage clinical programs and commercial assets. Their lead program, RG1068, is in Phase 3 trials for pancreatic imaging and could file for approval in 2011. RG2417, for bipolar depression, showed efficacy in a Phase 2a trial and expects Phase 2b results in Q1 2011. RepliGen is also developing treatments for orphan diseases and generates revenue from bioprocessing operations. Their goal is to advance their pipeline while maintaining a strong cash position to fund development.

1. RepliGen
RepliGen
NASDAQ: RGEN
Corporate Overview
October 2010

2. RepliGen Company Profile
Repligen acquires product candidates, advances them to a key inflection
point and captures value by commercializing or partnering
• Late-stage pipeline with significant market opportunity
– RG1068 to diagnose pancreatitis; >$100M U.S./E.U. market (Phase 3)
– RG2417 for bipolar depression; ~$2B market opportunity (Phase 2b)
– Two potentially transformative drugs for orphan CNS diseases; >$500M market
opportunity each (Pre-clinical)
• Financial sustainability
– Strong cash position (~$59M); low cash burn and no debt
– Profits from Bioprocessing business and royalties fund therapeutics pipeline
• Proven strategy
– Acquired patent from MIT; developed Erbitux® cell line; licensed to ImClone for $65M
– Acquired patent from Univ. of Michigan; developed Orencia® application; licensed to
Bristol-Myers for ~$65M(e) in royalties through 2013
Our goal for 2011 is to file an NDA in the U.S. and an MAA in the E.U. for RG1068,
secure partner for RG2417; assuming positive data in Q1 2011

3. RepliGen
Advancing Pipeline
Fueled by Commercial Assets
Pre-Clinical Phase 1 Phase 2 Phase 3
Market
Animal First Human Proof of Proof of
Therapeutic Product Models Trial Concept Efficacy
Pipeline
RG1068 Complete
Pancreatic Imaging Phase 3
RG2417 Complete
Bipolar Disorder Phase 2b
RG2833 Initiate
Friedreich’s Ataxia Phase 1
RG3039 Qualify clinical
Spinal Muscular Atrophy candidate
FY2011(e)
Commercial Assets
~$13M in
Bioprocessing revenue
Business
Biologics Purification ~$10M in
revenue
Orencia® Royalties
Rheumatoid Arthritis
= FY2011 Goal (03/31/11)

4. Pancreatic Imaging
Pre-RG1068 Post-RG1068
Biology Liver
Liver
RG1068 stimulates the
Bladder
Bladder release of fluid by the
pancreas; filling the Pancreas
Pancreas
Pancreas Pancreas
pancreatic ducts, which
makes them larger
Intestine Intestine
Pre-RG1068 Post-RG1068
Clinical Application
4-6 minutes post-RG1068
enhanced MRI leads to an
improved image of ducts;
diagnosis of pancreas
divisum which means
patient is a candidate
for surgery

5. RG1068 Phase 3 Highlights
• ERCP is an invasive, risky endoscopic procedure for diagnosis
of pancreatic duct abnormalities; associated with high morbidity
and measurable mortality
• Patients in the Phase 3 study were evaluated for detection of 10
pre-specified structural pancreatic abnormalities. MRI images
pre- and post-RG1068 were analyzed by three independent
radiologists; ERCP used as “truth standard”
– Radiologists evaluation of data was flawed due to significant deviations
from the protocol
– FDA and EMA agreed to a “re-read” of images using three new
radiologists
– Study showed that RG1068 aids in avoiding unnecessary ERCP; for
every patient on day of hospitalization from ERCP was saved
• Expect to complete Phase 3 re-read in Q1 2011
• If successful, file New Drug Application (NDA) in Q2/Q3 2011

6. Phase 3 Results
78%
74%
66%
60%
52%
46%
34% 35%
p<0.001 p<0.001 p<0.001 p<0.001
Enhanced image quality and duct visualization results in improved
sensitivity to detect abnormalities and confidence in diagnosis
*Sensitivity data is for Reader 1 only

7. Market Opportunity
Clinical Application U.S. E.U.
Abdominal MRI
200,000 150,000
Enhance existing MRI images
Endoscopy
Expand market opportunity; triage to appropriate 100,000 TBD
therapy and convert diagnostic endoscopy to MRI
• Market opportunity in U.S./E.U. for MRI enhancement is greater than
$100M, assuming a price of $350/vial
• Evaluating other clinical applications and market opportunity outside
of U.S./E.U.
– Surgery: improve confidence in diagnosis and pre-surgical planning
– New potential indication: pancreatic cancer detection/staging
– Japan is a third promising market; high utilization of MRI and potential for
favorable pricing

8. RG2417 for Bipolar Depression
• Bipolar disorder symptoms include episodes of severe
depression and mania; depressive episodes account for
majority of impairment
• Current therapies for bipolar depression are ineffective in
most patients and have significant side effects
• Bipolar disorder is linked to abnormal activity in the
mitochondria, the power plant of a cell
• RG2417, an oral formulation of uridine, may affect
mitochondrial activity and improve symptoms of depression
in bipolar disorder with minimal to no side effects

9. RG2417 Phase 2a Highlights
• Conducted a Phase 2a study resulting in statistically
significant improvement in depression on MADRS scale
– RG2417 well tolerated by patients; the adverse event profile for
RG2417 was equivalent to placebo
• Completed enrollment of Phase 2b study to confirm
Phase 2a results
• Expecting results from the Phase 2b study in the first
quarter of 2011
• Objective: license to a pharmaceutical partner in 2011

10. Phase 2a Results
All Patients Significant History of Symptoms
15 depressive episodes (n=33)
MADRS Score
MADRS Score
P= .03 .09 .01 .08 .22
P=0.01 (repeated measures) P<0.001 (repeated measures)

11. Market Opportunity
• Patients primarily seek treatment for the depressive symptoms
– Physicians report that 77% of the time patients seek treatement for
depressive symptoms as opposed to mania symptoms
• Psychiatrists have a high level of dissatisfaction with current
bipolar depression therapies because they are ineffective in
most patients and may have significant side effects
• Total costs of bipolar disorder ~$45 billion per year (NIH est.)
– Accounts for more than 16 million visits to a physician each year and
approximately 150,000 hospitalizations
• Worldwide prevalence >5 million
• Approximately $2B market opportunity (10% market
penetration)

12. RG2833 for Friedreich’s Ataxia
• Friedreich’s ataxia is an orphan
disease characterized by progressive
loss of muscle function which leads to
Frataxin Protein Level
incapacitation and loss of life
• Caused by a defective gene, which
results in low levels of Frataxin protein
• RG2833, an HDAC* inhibitor, is the
first compound to target activation of
the defective gene to increase
Patients Healthy frataxin production
Carriers
• >$500M market opportunity
A 2.5 fold increase in
Frataxin levels may be
sufficient to arrest *Histone deacetylase inhibitors (HDAC inhibitors) are a
class of compounds that interfere with the function of
disease progress histone deacetylase, which is related to gene expression

13. RG2833 Next Steps
• Initiate Phase 1 study following FDA approval
• Evaluate HDAC inhibitors in animal models of
Huntington’s disease and cognition
• Prosecute worldwide patent protection; composition
of matter patents; priority date May 2008

14. RG3039 for Spinal Muscular
Atrophy
• Spinal Muscular Atrophy (SMA) is an orphan disease characterized by
progressive loss of muscle function and early death in most patients
• Caused by a defective gene SMN2, which results in low levels SMN protein
• RG3039, is the first compound to target activation of the defective gene;
increasing the production of SMN and potentially arresting the progress of
the disease
• >$500M market opportunity
Disease Classification SMN2 Gene Copy Life Expectancy
SMA I 73% of patients have 2 copies ~2 Years
SMA II 82% of patients have 3 copies ~20 Years
50% of patients have 3 copies
SMA III 50 Years
and 45% have 4 copies
A 1.5 to 2 fold increase in SMN levels has the potential to profoundly
affect the course of the disease

15. RG3039 Next Steps
• Qualify RG3039 as a clinical candidate
– Complete GLP toxicology study to determine
appropriateness for human clinical trials
• Initiate Phase 1 study
• Seek funding from non-profits or NIH
• Prosecute composition of matter patent

16. Bioprocessing Overview
• For over 20 years, Repligen has been a leading supplier
of Protein A for production of monoclonal antibodies;
important therapies for cancer, autoimmune diseases
and osteoporosis
– OEM supply to GE Healthcare and Millipore
– FY2011 estimated revenue = ~$13M; 60% gross margin
• Repligen’s objective is to expand bioprocessing market
opportunity by broadening its product offering, and
through direct sales to end users
– Protein A Resins
– Pre-packed Columns
– Analytical Tools

17. Expanding Market Opportunity
Legacy Business
OEM suppliers End-users
Protein A • GE Healthcare • Monoclonals
• Millipore
Market Size $25M
Emerging Business
Protein A Protein A
Protein A Resins
Resins
End-users
Plug & Play Pre-Packed •Monoclonals
Chromatography Columns •Biologics
•Vaccines
Membranes
Analytical Tools
Market Size $500M

18. Bioprocessing Business
Large Scale Fermentation Large Scale Purification
rProtein A
“Plug and Play” Opus™ Analytical Tools
Affinity Resin
Columns ELISA Kits

19. Projected Orencia® Royalties
Licensed patent to Bristol-Myers for US sales of Orencia®, a novel
therapy for rheumatoid arthritis
$13.3
$12.8
Upfront payment
$6.3 for back-royalties $11.5
$10.3 $10.5
$9.0
$7.0
FY2011-FY2014 ~ $45M (e)

20. RepliGen
Corporate Assets
Pre-Clinical Phase 1 Phase 2 Phase 3
Market
Animal First Human Proof of Proof of
Therapeutic Product Models Trial Concept Efficacy
Pipeline
RG1068 Complete
Pancreatic Imaging Phase 3
RG2417 Complete
Bipolar Disorder Phase 2b
RG2833 Initiate
Friedreich’s Ataxia Phase 1
RG3039 Qualify clinical
Spinal Muscular Atrophy candidate
FY2011(e)
Commercial Assets
~$13M in
Bioprocessing revenue
Business
Biologics Purification ~$10M in
revenue
Orencia® Royalties
Rheumatoid Arthritis
= FY2011 Goal (03/31/11)

21. RepliGen Financials
FY2010(a) FY2011(e)
Ending: 3/31/2010 3/31/2011
Revenue $21M $24-26M
Net Loss ($4.1M) (<$3M)
EOY Cash* $59.1M $57-58M
Shares Outstanding (03/31/10) 30.8M
Shares & Vested Options (03/31/10) 32.2M
Market Cap (10/04/10) $104M
90 Day Average Volume (10/04/10) 45,000
* Net of acquisitions

22. RepliGen Upcoming News Stream
• September 2010: End of enrollment for RG2417
Phase 2b study
• November 2010: Presenting at Society for
Neurosciences on new indications for HDAC inhibitors
• November 2010: Q2FY11 results and quarterly update
• Q1 of 2011: Release RG1068 Phase 3 results
• Q1 of 2011: Release RG2417 Phase 2b study results
• H1 of 2011: Initiate phase 1 study of RG2833
• H1 of 2011: File IND for RG3039

23. RepliGen Why Invest in Repligen?
• Expecting data on a phase III development compound as
MRI contrast agent for the diagnosis of pancreatic duct
abnormalities in Q1, 2011
• Expecting data on a Phase II development compound for
bipolar disorder Q1, 2011
• ~$3 stock with $1.50/share in cash. Cash burn is less
than $0.10/share for 2011. No debt.
• Knowledgeable of monoclonal antibody production
process; holds 50% market share of protein A market

24. RepliGen Business Drivers
Advance Pipeline Accelerate
Bioprocessing
Shareholder
Value
Protect
Low Cash Burn
Innovation

25. RepliGen
Potential Back Up Slides

26. RepliGen Strategic Track Record
Acquired Developed Capture Value Value
Captured
Past
Compounds for cancer Erbitux® cell line Licensed to ImClone;$65M
treatment from MIT for National Cancer Institute settlement
Compounds for RA Orencia® cell line Licensed to Bristol-Myers;
From Univ. of Michigan Conducted early clinical trials ~$65M in royalties through 2013
Present and Future
Secretin for CNS diseases Completed Phase 3 study Commercialize (US) / Partner (EU);
from Univ. of Maryland for pancreatic imaging following FDA approval
Uridine as treatment for Completed Phase 2a study Following positive results, qualify
Bipolar Disorder Conducting a Phase 2b study potential partners
Compounds for Friedreich’s Filed New Drug Application Continue developing to capture
Ataxia from Scripps Research for RG2833 value as appropriate
Compounds for SMA from Identified clinical candidate Continue developing to capture
Families for SMA RG3039 value as appropriate

27. Phase 3 Trial and Results
• 258 patients were evaluated with MRI and ERCP for detection of 10
pre-specified structural abnormalities
Trial Protocol – ERCP used as “truth standard” for abnormalities
– MRIs analyzed by three independent radiologists
• Statistically significant improvements in the detection of structural
Primary Endpoints abnormalities using RG1068 enhanced MRI vs. MRI alone, with no
false positives
• Improvements in image quality, visualization of pancreatic ducts and
Secondary Endpoints confidence in diagnosis of abnormalities
• One out of the three radiologists achieved primary endpoints
– 256 additional days of hospitalization with ERCP
Results
• RG1068 well tolerated and safe vs. ERCP
• All three radiologists achieved secondary endpoints
• Radiologists evaluation of data was flawed due to significant
deviations from the protocol
Status • Food and Drug Administration (FDA) and European Medicines Agency
(EMA) agreed to a “re-read” of images using three new radiologists

28. Phase 2a Clinical Trial
A study with 83 patients, placebo-controlled, daily dosing
Protocol and weekly assessment for 6 weeks
• Statistically significant decreases in the symptom of
depression as measured by the Montgomery Asberg
Depression Rating Scale (MADRS) with minimal
Primary Endpoint side effects
• MADRS has been previously accepted by the FDA for
drug approvals in bipolar depression
• Statistically significant improvement in depression on
MADRS scale
• Well tolerated by patients; the adverse event profile for
Results
RG2417 was equivalent to placebo
• Clinical benefit demonstrated primarily in patients with
moderate-severe disease history

29. RepliGen Safe Harbor
This presentation contains forward-looking statements which are made pursuant to the safe harbor
provisions of Section 21E of the Securities Exchange Act of 1934. The forward-looking statements in this
presentation do not constitute guarantees of future performance. Investors are cautioned that statements in
this presentation which are not strictly historical statements, including, without limitation, statements
regarding current or future financial performance, management's strategy, plans and objectives for future
operations, clinical trials and results and product development and manufacturing plans and performance
such as the anticipated growth in the monoclonal antibody market and projected growth in product sales,
constitute forward-looking statements. Such forward-looking statements are subject to a number of risks and
uncertainties that could cause actual results to differ materially from those anticipated, including, without
limitation, risks associated with: the success of current and future collaborative relationships, the market
acceptance of our products, our ability to compete with larger, better financed pharmaceutical and
biotechnology companies, new approaches to the treatment of our targeted diseases, our expectation of
incurring continued losses, our uncertainty of product revenues and profits, our ability to generate future
revenues, our ability to raise additional capital to continue our drug development programs, the success of
our clinical trials, our ability to develop and commercialize products, our ability to obtain required regulatory
approvals, our compliance with all Food and Drug Administration regulations, our ability to obtain, maintain
and protect intellectual property rights for our products, the risk of litigation regarding our intellectual
property rights, our limited sales and manufacturing capabilities, our dependence on third-party
manufacturers and value added resellers, our ability to hire and retain skilled personnel, our volatile stock
price, and other risks detailed in Repligen's filings with the Securities and Exchange Commission. Repligen
assumes no obligation to update any forward-looking information contained in this presentation or with
respect to the announcements described herein.