<Page>
FILED BY COR THERAPEUTICS, INC. PURSUANT TO RULE 425 UNDER THE
SECURITIES ACT OF 1933 AND DEEMED FILED PURSUANT TO RULE 14a-12 OF THE
SECURITIES EXCHANGE ACT OF 1934.
SUBJECT COMPANY: COR THERAPEUTICS, INC.
COMMISSION FILE NO.: 000-19290
<Page>
Transcending the limits of medicine(SM)
[MILLENNIUM(C) logo(TM)]
Corporate Presentation for
Millennium / COR Therapeutics Merger
December 2001
(C) Millennium Pharmaceuticals, Inc.
<Page>
Statements in this presentation regarding the proposed transaction between
Millennium and COR, the expected timetable for completing the transaction,
future financial and operating results, benefits and synergies of the
transaction, future opportunities for the combined company, discovery and
development of products, potential acquisitions, strategic alliances and
intellectual property, and any other statements about Millennium or COR
management's future expectations, beliefs, goals, plans or prospects
constitute forward-looking statements within the meaning of the Private
Securities Litigation Reform Act of 1995. Any statements that are not
statements of historical fact (including statements containing the words
"believes," "plans", "anticipates," "expects," estimates and similar
expressions) should also be considered to be forward-looking statements.
There are a number of important factors that could cause actual results or
events to differ materially from those indicated by such forward-looking
statements, including: the inability to consummate the transaction, the
inability of Millennium to successfully integrate COR's operations and
employees; the inability to realize anticipated synergies and cost savings;
adverse results in drug discovery and clinical development processes; failure
to obtain patent protection for discoveries; commercial limitations imposed
by patents owned or controlled by third parties; dependence upon strategic
alliance partners to develop and commercialize products and services based on
our work; difficulties or delays in obtaining regulatory approvals to market
products and services resulting from the combined company's development
efforts; the requirement for substantial funding to conduct research and
development and to expand commercialization activities; and the other factors
described under the heading "Risk Factors That May Affect Results" in
Millennium's Quarterly Report on Form 10-Q for the quarter ended September
30, 2001, and under the heading "Risk Factors" in COR's Quarterly Report on
Form 10-Q for the quarter ended September 30, 2001, which descriptions are
incorporated by reference into this presentation. Millennium and COR disclaim
any intention or obligation to update any forward-looking statements as a
result of developments occurring after the date of this presentation.
<Page>
IMPORTANT ADDITIONAL INFORMATION WILL BE FILED WITH THE SEC Millennium plans
to file with the SEC a Registration Statement on Form S-4 in connection with
the transaction and Millennium and COR plan to file with the SEC and mail to
their respective stockholders a Joint Proxy Statement/Prospectus in
connection with the transaction. The Registration Statement and the Joint
Proxy Statement/Prospectus will contain important information about
Millennium, COR, the transaction and related matters. Investors and security
holders are urged to read the Registration Statement and the Joint Proxy
Statement/Prospectus carefully when they are available. Investors and
security holders will be able to obtain free copies of the Registration
Statement and the Joint Proxy Statement/ Prospectus and other documents filed
with the SEC by Millennium and COR through the web site maintained by the SEC
at www.sec.gov. In addition, investors and security holders will be able to
obtain free copies of the Registration Statement and the Joint Proxy
Statement/Prospectus from Millennium by contacting Gina Brazier or from COR
by contacting Shari Annes. Millennium and COR, and their respective directors
and executive officers, may be soliciting proxies from Millennium's or COR's
stockholders in connection with the transaction. A list of the names of
Millennium's directors and executive officers and descriptions of their
interests in Millennium is contained in Millennium's proxy statement dated
March 26, 2001, and its Annual Report on Form 10-K for the year ended
December 31, 2000, and its Current Report on Form 8-K dated December 6, 2001,
which documents are filed with the SEC. A list of the names of COR's
directors and executive officers and descriptions of their interests in COR
is contained in COR's proxy statement dated April 26, 2001, and its Annual
Report on Form 10-K for the year ended December 31, 2000, which documents are
filed with the SEC. A more complete description will be available in the
Registration Statement and the Joint Proxy Statement/Prospectus.
<Page>
AGENDA
- Building a major new biopharmaceutical company
- Terms of Merger
- Pipeline / Franchises
- Organization / Capabilities
- Financials
- Key Upcoming Events
<Page>
MILLENNIUM PHARMACEUTICALS, INC.
Vision
Transcending the Limits of Medicine(SM)
Mission
Create the Biopharmaceutical Company of the Future
Strategy
- Breakthrough Products
- Personalized Medicine / Productivity
- Value Creation
<Page>
BUILDING A MAJOR NEW BIOPHARMACEUTICAL COMPANY
<Page>
MILLENNIUM / COR THERAPEUTICS MERGER
Creating the Industry's Leading Biopharmaceutical Company Through:
- Integrated biopharmaceutical company: discovery to development to
commercialization (G2P)
- Demonstrated leadership in development and marketing of novel products
- 4 major franchise areas: cardiovascular, oncology, inflammation,
metabolic
- 3 products on the market
- 9 products in clinical development
- Sustainable pipeline fueling 3-4 NMEsin clinic in 2002
- Marketed breakthrough product - INTEGRILIN(R)
- #1 intravenous anti-platelet drug on the market
- >50% patient market share with potential for continued growth
<Page>
MILLENNIUM / COR THERAPEUTICS MERGER
Creating the Industry's Leading Biopharmaceutical Company Through:
- Significant new franchise area - cardiovascular
- Leading cause of mortality / single largest therapeutic area
- Key area of strength for both companies
- Expanded oncology franchise opportunity and discovery synergies in
inflammation and metabolic disease franchises
- Organization
- Skilled sales force and commercial infrastructure
- World-class research and development organization
- Management strength
<Page>
COMBINED ORGANIZATION WILL HAVE GREATER CAPACITY TO MAXIMIZE
PRODUCT OPPORTUNITIES
Benefits from Commercial Infrastructure
Benefits from Development Expertise
Benefits from Integrated Development and Commercial Capabilities
INTEGRILIN
- - #1 drug in class
- - Growing
- - Top-quality hospital salesforce
LDP-341 / J591
- - Potential breakthrough drugs in oncology
- - Recent positive data
- - Oncology drug development expertise
CT53518
- - New program in oncology
- - Drug CT53518
FactorXa MLN4760
- - Major new product opportunities
- - Genomic engine and research synergies
<Page>
TERMS OF MERGER
<Page>
TERMS OF MERGER
- - Stock-for-stock exchange valued at $2.0 B
- - COR Therapeutics shareholders will receive 0.9873 shares of newly-issued
Millennium common stock in exchange for each COR share
- - Implied purchase price of $35 per share (based on Millennium stock price at
close of business Wednesday, 12/5/01)
- - 77% premium to 12/5/01 close and a 64% premium to the 1 month average
- - Millennium to issue 58 M shares to current COR shareholders
- - Subject to Millennium / COR Therapeutics shareholder approval and HSR
clearance
- - Expected to close Q1 '02
<Page>
PIPELINE / FRANCHISES
<Page>
COMBINED PRODUCT DEVELOPMENT PIPELINE
<Table>
<Caption>
Cardiovascular
Oncology
Inflammation
MLN4760-Obesity LDP02-Crohn's Metabolic
LDP519-Stroke LDP02-UC
LDP01-Stroke LDP977-Asthma
Anti-CCR2
CCR1 LDP341-advanced Campath(R)-MS
CAB2 malignancies Melastatin(R)-
Melanoma
CT53518 LDP341-solid LDP341- Campath(R)-CLL
J591DM1 (combination) hematologic
Others J591RL- Prostate cancer INTEGRILIN- INTEGRILIN- INTEGRILIN-
CABG STEMI ACS/PCI
Pending
Clinicals Phase I Phase II Phase III / IV Launched
2002
</Table>
<Page>
FRANCHISE: CARDIOVASCULAR
Products -INTEGRILIN Unstable angina / NSTEMI / PCI
Clinical -INTEGRILIN STEMI, CABG
Preclinical / Late Lead -Factor Xa Inhibitor-Deep vein thrombosis /
atrial fibrillation
-Platelet ADP Receptor Antagonist-arterial
thrombosis
-PDGF inhibitor-restenosis / atherosclerosis
Expertise -Platelet biology
-Blood coagulation
-Growth Factor Receptors
-Endothelial Cell and Cardiac Myocyte biology
Partnerships -Schering-Plough, Lilly, Bayer
Market Opportunity -Single largest therapeutic category with
$40 B in 2000 sales
<Page>
INTEGRILIN (EPTIFIBATIDE):
#1 INTRAVENOUS ANTI-PLATELET AGENT
- -INTEGRILIN
-Launched May 1998 for acute coronary syndromes, PCI
-New INTEGRILIN guidance: Reforecasted at $225-230 M / year worldwide
for 2001
->30% growth
-Market leaderwith >50% patient market share
~100 U.S. sales reps
-In Phase II IV trials for expanded labeling
- STEMI
- CABG
-Major product with estimated peak year sales of $400-600 M
[(eptifibatide) Injection
INTEGRILIN LOGO]
<Page>
<Table>
<Caption>
FRANCHISE: ONCOLOGY
Products - Campath(R) -- Refractory CLL
- Melastatin(R) -- Malignant melanoma diagnostic
Clinicals - LDP341 -- Multiple cancers
- J591RL -- Prostate cancer
Preclinical/ Late-Lead - CT53518
- J591DM1
- Multiple Programs
Expertise - Proteasome - Therapeutic antibodies
- Intracellular kinases - Diagnomics/pharmacogenomics
- Receptor tyrosine kinases
Partnerships - Bayer - BD
- Lilly - Berlex/Schering/Ilex
- BMS - BZL
</Table>
<Page>
LDP341: HEMATOLOGIC MALIGNANCIES AND SOLID TUMORS
Phase II studies in Multiple Myeloma (MM)
- Refractory MM: 75 patients, accrual completed
- First line relapse MM: 64 patients, accrual ongoing
Phase II study in Chronic Lymphocytic Leukemia (CLL)
- Refractory CLL: 64 patients, accrual ongoing
Phase I combination studies in solid tumors
- Gemcitabine (pancreas and lung):
MGH, 50 patients, accrual ongoing
- Irinotecan (gastrointestinal):
MGH/UNC, 56 patients, accrual ongoing
Other combination studies planned
- Taxanes (lung, prostate, and breast):
To be initiated Q4 2001
- Additional agents being evaluated through investigator sponsored trials
and CTEP (NCI)
<Page>
LDP341: HEMATOLOGICAL MALIGNANCY AND SOLID TUMORS
RESULTS TO DATE
- - Over 200 patients treated in 6 Phase I studies (3 MLNM, 3 NCI)
- - Generally well tolerated with manageable side effects
- - Objective responses:
- In a variety of solid tumors (prostate, lung, kidney, others)
- In refractory myeloma and related diseases (7 out of 10)
and non-Hodgkin's lymphoma
-Anti-tumor activity and decreased M-protein levels
- - Pharmacogenomics program: 80% of Phase II collecting DNA
- - Preliminary Phase II data at ASH
<Page>
FRANCHISE: INFLAMMATION
Clinicals - LDP02 -- IBD - LDP519 -- Stroke
- LDP977 -- Asthma - LDP01 -- Stroke
Preclinical/ Late-Lead - Anti-CCR2 - CCR1
- PDGF receptor antagonists -- - CAB-2
fibroinflammatory diseases - Aventis-Millennium
Expertise - Leukocyte activation/differentiation: kinases,
co-stimulation
- Leukocyte migration: chemokines, integrins
- Tissue damage and repair: leukotrienes, TNF
- Modulation of repair response to inflammation
Partnerships - Aventis - Taisho - XOMA
- Genentech - Roche
<Page>
FRANCHISE: METABOLIC
Clinicals - MLN4760 -- Obesity, first genomically-derived target
entered human clinicals Nov.'01
Preclinical/ Late-Lead - MC4
- STG-A-MDCHR
Expertise - Key pathways in metabolic / diabetes research
- Hunger / Satiety - Insulin Resistance
- Thermogenesis - Insulin Secretion
- Absorption
Partnerships - Abbott
<Page>
ORGANIZATION / CAPABILITIES
<Page>
COMMERCIALIZATION AND MANAGEMENT
- - Well-regarded management team with proven record of success, including
- Vaughn Kailian, Vice Chairperson
- Charles Homcy, MD, President, Research and Development
- - Clinical, regulatory and commercial marketing and sales force and
infrastructure
- Seasoned development and commercialization team with track record of
excellence
- - Critical mass
- Total 1800 employees
- 1200 in R&D
- 140 in commercial
- - 2002 R&D budget of ~$500 M
<Page>
ORGANIZATIONAL STRUCTURE
[EDGAR REPRESENTATION OF FLOWCHART]
CEO & Chairperson
Mark Levin
Commercial
Vaughn Kailian
Vice Chairperson
Strategic Product Dev
John Maraganore
Marketing
Bob Terifay
Commercial Ops
Paul Hamelin
Sales
Bonnie Zell
Research & Development
Charles Homcy, President, R&D
Discovery
Bob Tepper
Disease Biology
Cardiovascular
Oncology
Metabolic
Inflammation
Drug Discovery
Pre-Clinical
Biotherapeutics
Development
Clinical
Regulatory
QA/QC
Business
Kevin Starr, COO
Corporate Communications
Clare Midgley
Legal
Worldwide Mfg
Corporate Dev
HR
Finance
Operations
IT
Millennium Limited
Productivity
Allan Marchington
CTO
Mike Pavia
Technology
Craig Muir
Patient Management
Ken Conway
<Page>
FINANCIALS
<Page>
FINANCIAL STRENGTH: COMBINED COMPANIES
- - INTEGRILIN forecasted to achieve $225-230 M in worldwide sales in 2001
- - Millennium 2001 financial guidance unchanged
- - $2.0 billion in cash
- - Important step toward breakeven in 2003/4
- - Engine to power growth into top 10 biopharmaceutical companies
<Page>
2001 FINANCIAL GUIDANCE
<Table>
<Caption>
Millennium COR Therapeutics
---------- ----------------
Revenue ($) 220-240 M ~130 M
R&D Expense ($) 375-400 M 40 M
FTEs 1500 321
Cash ($) 1.5 B 630 M
Products:
Market 2 1
Clinic 8 1
FIP for 2002 2-3 1-2
</Table>
<Page>
KEY UPCOMING EVENTS
<Page>
KEY UPCOMING EVENTS
- - LDP341 preliminary Phase II data at ASH, Dec. 10, 2001
- - Advance clinical programs:
- Initiating Phase III trials for INTEGRILIN - facilitated angioplasty for
ST-segment elevation MI
- Initiation of Phase I LDP341 combination studies with Taxotere
- Initiation of Phase I study of CT53518 in acute myeloid leukemia
- - Continue pace of transforming relationships:
- M&A
- In-licensing and partnerships
- -Integrate and build on COR Therapeutics' capabilities
<Page>
BACK-UP SLIDES
<Page>
BUILDING THE BIOPHARMACEUTICAL COMPANY OF THE FUTURE:
CARDIOVASCULAR FRANCHISE
<Page>
[INTEGRILIN(R) logo]
SETTING THE STANDARD OF CARE IN ACUTE CORONARY SYNDROME
<Page>
INTEGRILIN (eptifibatide): PRODUCT PROFILE
- - Broadest approval in GPIIb - IIIa inhibitor class
- - Robust efficacy in PCI (ESPRIT trial)
- - Breadth, depth, persuasiveness of PURSUIT unstable angina data
- - Safety: minimal bleeding and thrombocytopenia concerns
- - PK / PD: fast onset and rapid reversibility
- - Ease of use: ready-to-use 8-hour vials
- - Cost-effective
<Page>
INTEGRILIN (eptifibatide): COMPETITIVE STRENGTH
<Table>
<Caption>
Indication / Uses INTEGRILIN ReoPro(R) Aggrastat(R)
(abciximab) (tirofiban HCl)
Limited to
U A/N STEMI - Refractory UA -
(early aggressive strategy) Awaiting PCI
UA/N STEMI without PCI - -
(early conservative strategy)
Elective PCI - -
Urgent/ emergency PCI - -
</Table>
<Page>
Silde depicting a line graph showing Death and mycardial infarction at 1 year
of placebo (n=1,024) against Integrilin (n=1,040) (where P=0.0010), with
results at approximately 12 months of 10.2% for Placebo and 6.47% for
Integrilin and RRR of 37%.
<Page>
Slide depicting a line graph showing incidence of death or myocardial
(re-)infarction over 30 days of placebo (n=1,766) against Eptifibatide
(n-1,756) (where P=0.003), with results of 15.4% for Eptifibatide (n=1,756)
and 11.9% for Eptifibatide.
<Page>
INTEGRILIN (eptifibatide): The Market Leader
Total Patient Share
(n=1,600,000 proj.)
<Table>
<Caption>
1ST QTR 2ND QTR 3RD QTR 4TH QTR
------- ------- ------- -------
East 26.1 10.5 14.8 49.3
West 30.6 38.6 34.6 31.6
North 45.9 46.9 45 43.9
</Table>
GP IIb-IIIa Inhibitor Share
(n=824,350 proj.)
<Table>
<Caption>
1ST QTR 2ND QTR 3RD QTR 4TH QTR
------- ------- ------- -------
East 51 20 29 49.3
West 30.6 38.6 34.6 31.6
North 45.9 46.9 45 43.9
</Table>
<Page>
INTEGRILIN (eptifibatide): Growth Opportunities
- - Increase duration of therapy by establishing early use, i.e., early
aggressive strategy
- - Increase number of patients treated currently estimated at 700,000 out
of total market of 1,600,000
- - Increase number of hospitals ( "drip and ship" feeder hospital use)
- - Continue seizing share from ReoPro and Aggrastat
- - New indications
- ST-segment elevation MI
- CABG surgery
<Page>
INTEGRILIN(R)(eptifibatide):
CONTINUED GROWTH POTENTIAL
<Table>
<Caption>
Market Segment/ 2000 2001 2002 2003
Size Estimate Projection Projection Projection
-------- ---------- ---------- ----------
UA/NSTEMI - Class Share 68% 74% 77% 79%
with PCI - INTEGRILIN(R) 34% 46% 54% 59%
(325,000) - % pre-PCI use 45% 50% 60% 65%
- % at PCI 55% 50% 40% 35%
- Duration
- pre-PCI use 33 hours 32 hours 33 hours 33 hours
- at PCI use 21 hours 17 hours 18 hours 18 hours
UA/NSTEMI - Class Share 21% 26% 28% 32%
without PCI - INTEGRILIN(R) 49% 55% 61% 64%
(910,000) - Duration 33 hours 33 hours 33 hours 33 hours
Other PCI - Class Share 51% 64% 68% 70%
(375,000) - INTEGRILIN(R) 45% 56% 64% 69%
- Duration 21 hours 17 hours 18 hours 18 hours
</Table>
<Page>
INTEGRILIN (EPTIFIBATIDE): COMMERCIAL STRENGTH
- - Three sales forces totaling (370 representatives)
- COR Therapeutics, Inc.
- Schering-Plough
- Genentech
- - Covering > 4,000 hospitals, over 85% of the available patients
<Page>
FACTOR XA PROGRAM
Opportunity
- Orally active small molecule inhibitor
- Target is patient and physician dissatisfaction with Coumadin
Key Feature
- Predictable PK/PD, minimal food (alcohol) effect, benign toxicology profile
(No need for monitoring)
- Novel treatment for DVT; arterial thrombosis; atrial fibrillation
Status
- Preclinical
- Potent, selective, orally active inhibitors
- Proof-of-concept in animal models
- >4,000 compounds made using ~ 20 scaffolds
<Page>
ADP PROGRAM
Opportunity
- To develop a "new generation" oral platelet ADP receptor antagonist
- Chronic agent for the prevention of ischemic events in patients who've
experienced stroke, MI, UA and PAOD
Key Feature
- Orally active small molecule competitive antagonist
- Direct acting, rapid onset, reversible inhibitor
- Provide consistent ("50%) inhibition of platelet aggregation with improved
efficacy vs. aspirin
Status
- Advanced chemistry program has identified a lead series
<Page>
BUILDING THE BIOPHARMACEUTICAL COMPANY OF THE FUTURE:
ONCOLOGY FRANCHISE
<Page>
CAMPATH(R)
- - U.S. launch June, 2001
- - European launch July, 2001
- - Restructure ownership in Campath(R)
- Accelerate income for Millennium up to $140 M
- Share in future potential of Campath(R)
- Royalties
<Page>
ANTI-PSMA ANTIBODY (J591)
PROSTATE SPECIFIC MEMBRANE ANTIGEN
Opportunity
- - Prostate cancer ([approx]180,000 new cases in US)
- - Prostate-cancers express PSMA on cell surface
Key Features
- - PSMA expressed in most prostate tumors (primary and metastatic) expression
increases with tumor progression
Status
- - Developing both radiolabeled and immunotoxin conjugates for prostate cancer
- - Phase I clinical trials underway in patients with advanced prostate and
non-prostate cancers
Results to date
- - Radiolabeled anti-PSMA
- >60 patients treated to date
- PSA expression and tumor mass reduction
- Effective tumor imaging in patients
- Antibody is well-tolerated
<Page>
RECEPTOR TYROSINE KINASE PROGRAM
Opportunity
- Novel treatment for acute myeloid leukemia
- Intervention of a key pathway (FLT3 receptor) with application in other
malignancies
Key Features
- Potent, selective orally active small molecule antagonists of PDGF, FLT3,
and related family member
- Targeted medicine to achieve improved therapeutic index
Status
- CT53518 FIP in early 2002
- Inhibition of tumor growth in animal models
<Page>
BUILDING THE BIOPHARMACEUTICAL COMPANY
OF THE FUTURE
COMMERCIAL ORGANIZATION
U.S.
- Commercial Development
- Market Research
- Medical Affairs
- Marketing
- Sales
Europe
- Growth Opportunity
<Page>
U.S. SALES FORCE REGION ALIGNMENT
[MAP]
NORTHEAST
NORTH CENTRAL
WEST
MID-WEST
METRO
SOUTHWEST
MID-ATLANTIC
SOUTHEAST
FL.
- - Seasoned sales force
- Average 10 years experience
- Technical product experience
- - Focus on major teaching and high-volume community hospitals
<Page>
VALUE CREATION
<Page>
MILLENNIUM: THE BIOPHARMACEUTICAL COMPANY OF THE FUTURE
GOAL: $100B + ANNUAL RETURN
Valuation Model
Productivity
Pipeline
- - Advancing clinical products
- - 4 franchise areas
- - Robust preclinical
- - R&D
Platform
- - Comprehensive
- - Integrated
- - Industrialized
Organization
- - Downstream capabilities
- - Critical mass and scale
- - Flexibility
M&A / Licensing
- - Alliances
- - Partnerships
- - 50-50 ownership
<Page>
MILLENNIUM: THE BIOPHARMACEUTICAL COMPANY OF THE FUTURE
<Page>
IMPORTANT ADDITIONAL INFORMATION WILL BE FILED WITH THE SEC
Millennium plans to file with the SEC a Registration Statement on Form S-4 in
connection with the transaction and Millennium and COR plan to file with the
SEC and mail to their respective stockholders a Joint Proxy
Statement/Prospectus in connection with the transaction. The Registration
Statement and the Joint Proxy Statement/Prospectus will contain important
information about Millennium, COR, the transaction and related matters.
Investors and security holders are urged to read the Registration Statement
and the Joint Proxy Statement/Prospectus carefully when they are available.
Investors and security holders will be able to obtain free copies of the
Registration Statement and the Joint Proxy Statement/ Prospectus and other
documents filed withthe SEC by Millennium and COR through the web site
maintained by the SEC at www.sec.gov.
In addition, investors and security holders will be able to obtain free
copies of the Registration Statement and the Joint Proxy Statement/Prospectus
from Millennium by contacting Gina Brazier or from COR by contacting Shari
Annes.
Millennium and COR, and their respective directors and executive officers,
may be soliciting proxies from Millennium s or COR s stockholders in
connection with the transaction. A list of the names of Millennium s
directors and executive officers and descriptions of their interests in
Millennium is contained in Millennium's proxy statement dated March 26, 2001,
and its Annual Report on Form 10-K for the year ended December 31, 2000, and
its Current Report on Form 8-K dated December 6, 2001, which documents are
filed with the SEC. A list of the names of COR sdirectors and executive
officers and descriptions of their interests in COR is contained in COR s
proxy statement dated April 26, 2001, its Annual Report on Form 10-K for the
year ended December 31, 2000 and its Current Report on Form 8-K dated
December 6, 2001, which documents are filed with the SEC. A more complete
description will be available in the Registration Statement and the Joint
Proxy Statement/Prospectus.