<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 ACT OF 1934. SUBJECT COMPANY: COR THERAPEUTICS, INC. COMMISSION FILE NO.: 000-19290 Transcending the limits of medicine -SM- [MILLENNIUM LOGO] Mark J. Levin Chairperson and Chief Executive Officer JP Morgan H&Q 19th Annual Healthcare Conference San Francisco, CA January 10, 2002 -C- 2001 Millennium Pharmaceuticals, Inc. <Page> This presentation contains "forward-looking statements," including statements about our growth and future operating results, discovery and development of products, potential acquisitions, strategic alliances and intellectual property. Various risks may cause Millennium's actual results to differ materially, including: adverse results in our drug discovery and clinical development processes; failure to obtain patent protection for our discoveries; commercial limitations imposed by patents owned or controlled by third parties; our 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 our development efforts; and the requirement for substantial funding to conduct research and development and to expand commercialization activities. For a further list and description of the risks and uncertainties we face, see the reports we have filed with the Securities and Exchange Commission. We disclaim any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. <Page> IMPORTANT ADDITIONAL INFORMATION WILL BE FILED WITH THE SEC Millennium has filed 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 the Investor Relations group at each company. 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, its Annual Report on Form 10-K for the year ended December 31, 2000 and its Current Report on Form 8-K dated December 7, 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. <Page> Agenda - Vision - Mission - Strategy - Creating the Leading Biopharmaceutical Company - Franchise and Pipeline Highlights - 2001 Accomplishments - 2002 Goals and Beyond - Delivering on the Promise <Page> Vision - Mission - Strategy: Creating the Leading Biopharmaceutical Company <Page> Millennium Pharmaceuticals, Inc. Vision Transcending the Limits of Medicine -SM- Mission Create the Leading Biopharmaceutical Company Strategy - Breakthrough Products: Sustainable Pipeline - Franchise Businesses - Personalized Medicine and Productivity - Value Creation <Page> Breakthrough Products: Sustainable Pipeline - Franchise Businesses - - Four major franchises - - Two therapeutic products on market - Campath (Registered Trademark) - INTEGRILIN (Registered Trademark) - - 10 molecules in clinical trials - - Discovery engine to deliver a sustainable pipeline <Page> Sustainable Pipeline Genome Transcriptome Proteome Molecular Pathways HTS / Year 75+ NMEs to Clinic / Year 2002: 3-4 2005+: 5+ NMEs to Market / Year 2003 / 4: 1 2005 / 6: 1-2 <Page> Integrated G2P Platform: More High Quality Products Chips Proteomics Imaging Fluidics Structure Predictive ADMET CDU SNP Gene/Target Identification Target Validation Lead Identification Lead OP Preclinical Clinical Trials Commercial and Patient Management Process Development / Manufacturing Biology Markers Computational Biology Chemistry Chemical Genetics Computational Chemistry Patho-pharmacology Pharmaco-genomics Patient Management - Process - Platform - Knowledge Management - Bottlenecks <Page> Product Development Pipeline <Table> <Caption> Clinical Candidates Phase I Phase II Phase III Marketed / 2002 Phase IV Cardiovascular Xa MLN519 INTEGRILIN(R) INTEGRILIN(R) INTEGRILIN(R) CAB2 MLN01 - CABG - STEMI - ACS/PCI Oncology CT53518 MLN341 - Solid MLN341 - MM Campath(R)--CLL MLN591DM1 MLN591RL MLN341 - CLL MLN944 MLN576 CT53608 Inflammation CCR2 MLN02 - Crohn's CCR1 MLN02 - UC CCR5 MLN977 - Oral MLN273 Metabolic STG-A-MD MLN4760 </Table> <Page> Personalized Medicine --> Productivity <Table> <Caption> Franchise Areas Cardiovascular Oncology Inflammation Metabolic Dis. Genomic Tissues Technologies Transcriptional Profiling Large Scale Pathology The Right Gene Informatics Molecular Thrombosis Cell Cycle Chemokines CNS Metabolism Pathways Angiogenesis Proteosome Cards Leptin Pathway The Right Target Myocyte Apoptosis Apoptosis Gut Biochemistry Classes of Integrins Kinases Kinases GPCRs Molecules Ion Channels Proteases GPCRs Transporters The Right Drug GPCRs Antibodies Antibodies Proteases Disease Tissue / Patients / Markers The Right Patients Imaging / Outcome Data </Table> <Page> Combined Commercial Organization <Table> <Caption> Today Add The Future Breakthrough - Cardiovascular - Inflammation - 4 significant Products - Oncology - Metabolic therapeutic franchises Geographic - US cardiology - Expand US presence - Global presence Presence and hospital - Initiate European in 70% worldwide presence commercialization effort market - Partner Japan Strategic - Commercial - Medical science liaisons - Critical mass to Marketing infrastructure - Pharmacogenomics establish market - Product leadership development - Personalized medicine - Commercial intelligence - Medical affairs - Web / internet commerce - Business analysis </Table> Scalability of Capabilities, Geographic Presence --> Access New Products <Page> Millennium Commercial Vision - - Personalized medicine products - - Focused on unmet needs - - Knowledge network in a customer marketing model - - Pioneering utilization of communication technology (web / internet) - - Broad customer definition - - Novel integration of global organization in 70% of worldwide market VALUE CREATION & EXCELLENCE <Page> Biopharmaceutical Company of the Future $100 Billion <Table> <Caption> Personalized Value Pipeline Medicine / Creation Organization Productivity 2 Therapeutics Discovery leadership 4 Franchises 1200 R&D products Discovery -> Clinic Aventis, Abbott, $500+ M R&D '02 10 clinicals - Structure Schering, Bayer Business Leadership 3-4 NMEs in clinic '02 - ADMET 4 M&A ('97-'01) - CDU Commercial Leaders 5+ NMEs in clinic '05 -> - PGx 3 Inlicensing ('01) in ACS / PCI 1-2 products per Knowledge Strong balance People Focus year '05 / '06 -> Management sheet </Table> <Page> Franchise and Pipeline Highlights <Page> Franchise Leadership - Building a Business <Table> <Caption> Cardiovascular Oncology Inflammation Metabolic Disease Worldwide Market $40 B >$20 B $25 B $10 B Indication ACS, PCI, 1(degree)/ 2(degree) Hematologic RA, Asthma, Obesity, type II prevention of MI, and solid IBD, MS, diabetes CABG, CHF tumors COPD, HIV Commercialization Millennium Millennium Millennium Millennium US & Europe US & Europe Aventis Abbott R&D Investment 160 FTEs, 560 FTEs, 530* FTEs, 300* FTEs, $60 M $200 M $130 M $60 M </Table> *FTEs include partner efforts <Page> Cardiovascular Franchise [GRAPHIC] <Page> Mediators of Platelet Activation, Aggregation & Ischemic Complications of PCI [GRAPHIC] <Page> Franchise: Cardiovascular Products - INTEGRILIN(R)- Unstable angina / NSTEMI / PCI Clinical - INTEGRILIN(R)- STEMI, CABG - MLN01 - Reperfusion injury - MLN519 - Reperfusion injury 2002 Clinical Candidates - Factor Xa Inhibitor - CAB2 Expertise - Thrombosis/ACS, Primary and Secondary MI Prevention - Cardiac myocyte biology / CHF - Growth factor receptors and endothelial cell biology/ vascular disease Market Opportunity - Single largest therapeutic category with $40 B in 2000 sales <Page> INTEGRILIN #1 Drug for Acute Coronary Syndromes and PCI - Glycoprotein IIb / IIIa inhibitor - Small molecule [illus. from VK to go here] #1 Intravenous Antiplatelet Agent - - $230 M in 2001 sales - 34% growth vs. 2000 - - Market leader with >50% patient market share - - >30% annual growth with >$500 M peak sales - - Partnership with Schering Plough - - Three sales forces totaling 370 representatives [INTEGRILIN LOGO] <Page> INTEGRILIN: Strategies to Facilitate 30% Growth - - Seize market share from competitive GPIIb-IIIa inhibitors - Competitive conversion effort with top 100 competitive hospitals - Major medical education symposia for interventional cardiologists - Investigator-initiated studies focused on differentiation - - Drive market growth outside of the cath lab - CRUSADE in 60,000 unstable angina patients - ADVANCE MI in 6,000 patients presenting with heart attack - MSL program to establish treatment guidelines <Page> Factor Xa Inhibitor Program Opportunity - Oral anticoagulant therapy - Replacement for Coumadin / Warfarin - Novel treatment for DVT; atrial fibrillation; prosthetic valves (3-4 M patients / year) Key Features - Long half-life, high oral availability - Predictable PK / PD, minimal food effect (no need for monitoring) - Favorable safety Status - Preclinical - Broad series of potent and selective inhibitors - Clinical lead selected: CT54004 - Proof-of-concept in animal models - 2002 clinical candidate <Page> Cardiovascular Franchise Additional Programs: <Table> <Caption> Program Mechanisms Status Lead Indications MLN01 Anti-CD18 Phase I Reperfusion injury CAB2 Complement Preclinical CABG complications inhibitor Platelet ADP Platelet receptor Lead Optimization Primary and secondary receptor inhibitor MI prevention, stroke PDGF receptor RTK Lead Vascular proliferative Optimization disease </Table> Personalized Medicine Initiatives: - - Major marker study with Eric Topol, M.D., Cleveland Clinic - 500 CVD patients / 500 patients - 300 SNPs genotyped - 27 SNPs / Haplotypes with association - - Pharmacogenomics in ADVANCE MI <Page> Oncology Franchise [GRAPHIC] <Page> Franchise: Oncology Products - Campath(R) - Refractory CLL - Melastatin(R) - Malignant melanoma diagnostic - MLN341 - Multiple cancers Clinical - MLN591RL - Prostate cancer - MLN576 - Solid tumors 2002 Clinical Candidates - MLN591DM1 - CT53518 - CT53608 - MLN944 - MLN273 - Bayer programs Expertise - Proteasome - Therapeutic antibodies - Intracellular kinases - Diagnomics/pharmacogenomics - Receptor tyrosine kinases Market Opportunity - The leading area of unmet medical need <Page> MLN341: Proteasome Inhibition Major new element of oncology intervention - New mechanism - Novel pathway - Broad applications - Broad IP estate [GRAPHIC] <Page> MLN341 Refractory Multiple Myeloma: Preliminary Phase II Data Efficacy Safety - - Heavily pretreated and - MLN341 well tolerated refractory patient population - Common side effects are - Patients progressing at study entry manageable (nausea, diarrhea - Median survival 6-12 months and thombocytopenia) - Universally fatal - Grade 3 peripheral neuropathy - - 85% stable or improved occurred in 3 patients (3%) - - 52% response rate after 2 cycles - LESS THAN 10% patients of therapy discontinued due to any - - 11% confirmed complete and adverse events near complete responses observed <Page> MLN341: Complete Response in Multiple Myeloma [GRAPH] Prior Therapies: - 14 prior transplants; Ch 13 abnormal - MP, VAD, Mel/PBSC x 3, dexamethasone - Gemzar, DCEP, dendritic vaccine - Thalidomide, DCEAP, Doxil/Navelbine <Page> MLN341: Clinical Program Ongoing Phase I studies: - - Gemcitabine (pancreas and lung) -- 50 patients, accrual ongoing - - Irinotecan (gastrointestinal -- 56 patients, accrual ongoing New Phase I studies: Taxotere (lung, prostate, and breast) Planned clinical studies - - Phase III multiple myeloma -- 1H 2002 - - Multiple solid tumor pivotal trials -- `02 - '03 <Page> Anti-PSMA Antibody (MLN591) Prostate Specific Membrane Antigen Opportunity Status - - No effective therapies for - Phase I -- RL clinical trials in hormone refractory disease advanced prostate and non-prostate cancers - Initiate Phase I DM1 and Phase II RL Key Features studies -- 2002 - - PSMA expressed in most prostate tumors Results to date - - Expression increases with - Radiolabeled anti-PSMA tumor progression - GREATER THAN 60 patients treated to date - Antibody is well-tolerated - PSA levels and tumor mass reduction <Page> MLN591RL in Refractory Prostate Cancer MLN591RL Dose [GRAPH] Patient had GREATER THAN 50% decrease in PSA level <Page> Oncology Pipeline Additional Programs: <Table> <Caption> Program Mechanism Status Lead Indications MLN576 Dual Topo I / II Phase I Solid tumors CT53518 RTK IND filed AML MLN944 Dual Topo I / II Preclinical Solid tumors MLN591DM1 Anti-PSMA Preclinical Prostate cancer CT53608 RTK Late Lead Glioblastoma </Table> Personalized Medicine Initiatives: - Diagnomic program with BD / Tripath (e.g., Melastatin(R)) - Pharmacogenomics on clinical programs - MLN341 - MLN591 - CT52518 <Page> Inflammation Franchise [GRAPHIC] Leukocyte Activation/ Tissue Damage/ Differentiation Migration Repair <Page> Franchise: Inflammation Clinical - MLN02 - Crohns, UC - MLN977 Oral - Asthma 2002 Clinical Candidates - CCR2 - CCR5 - CCR1 (Aventis) - MLN273 Preclinical - MLN977 Inhalation - CT54141 Expertise - Leukocyte activation/differentiation: kinases, co-stimulation - Leukocyte migration: chemokines, integrins - Tissue damage and repair: leukotrienes, TNF, fibrosis Partnerships - 50-50 with Aventis Market Opportunity - Major markets in asthma, fibrosis (e.g. cirrhosis), RA, IBD, MS and COPD <Page> Inflammation Pipeline Program Status Lead Indications Partner CCR1 Preclinical RA, MS CCR2 Preclinical RA, MS MLN977 Preclinical Inhalation-asthma CCR5 Preclinical HIV CT54141 - PDGF Late Lead Fibroinflammatory ? Receptor disorders, pulmonary fibrosis and hepatic cirrhosis <Page> Metabolic Franchise [GRAPHIC] <Page> Franchise: Metabolic Clinical - MLN4760 - Obesity, 1st genomically-derived target in clinic 2002 Clinical Candidates - STG-A-MD - obesity Preclinical - MC4 agonist - FATP4 - MC4 antagonist Expertise - Key pathways in metabolic / diabetes research - Hunger / Satiety - Insulin Resistance - Thermogenesis - Insulin Secretion - Absorption Partnerships - Worldwide 50-50 with Abbott Market Opportunity - Obesity - largest future market <Page> MLN4760 Opportunity - 1st genomics program to clinic from Millennium-Abbott alliance Key Features - Inhibits novel carboxypeptidase - Non-appetite suppressant mechanisms Status - Phase I clinical trial for PK / PD and safety - 56 subjects, accrual ongoing Results to date - Preclinical data support favorable change profile in metabolic <Page> 2001 Accomplishments <Page> 2001 Accomplishments Products - Campath(R) on market - US, Europe - - INTEGRILIN(R) - #1, >50% share, +34% Clinic - - 10 molecules in clinic (and 1 IND filed) - - MLN341 - Phase II trials, Phase I trials - - MLN977 Oral - Phase II - - MLN02 - Phase II - - MLN591RL - Phase I - - MLN576 - Phase I Phase I Pipeline - - 84 HTS Value Creation - - COR Merger - - Metabolic Disease: 50/50 worldwide Abbott - - In/Out-licensing - PSMA, TOPO 1 / 2, GC-C, CAB2 / MLN01, Campath(R) - - 200+ issued patents, 2000+ applications - - $2.1 B cash / $700 M debt Productivity - - Leading discovery effort - - Alliances: Affymetrics, SGI, Caliper, Pharsight, Abbott - - Knowledge management, CDU initiative underway <Page> 2002 Goals <Page> 2002 Goals: Creating a Major Biopharmaceutical Company Sustainable Pipeline - - 3-4 NMEs first in clinic 2002 - - 75 HTS - - $500+ M R&D investment in 4 key franchises Oncology Franchise - - MLN341 to start Phase III - 1H 2002 - - MLN591RL in Phase II - 2H 2002 - - 3-4 additional NMEs in clinical trials Cardiovascular Franchise - - INTEGRILIN(R)sales $300 M - - Xa in clinic - 2H 2002 Inflammation Franchise - - Advance clinical pipeline - - End 2002 with 4-5 NMEs trials (ongoing) <Page> 2002 Goals: Creating a Major Biopharmaceutical Company Value Creation - Revenue $420 M - $175-200 M NOL, on track for breakeven 2004 - >$1.7 B in cash with ~$250 M debt - Continued M&A and transforming alliances Personalized Medicine / Productivity - Pharmacogenomics in 6 clinical programs <Page> Millennium: Fully Integrated Gene-to-Patient Biopharmaceutical Company - Delivering on the promise of molecular medicine to create the next era of therapeutic breakthroughs to make a difference in people's lives - Sustainable product pipeline - Personalized Medicine and Productivity - Business leader in transforming relationship - Strong financial position - Transforming commercial marketplace - Critical mass -> capabilities <Page> Millennium: The Biopharmaceutical Company of the Future