system: You are a contract-analysis assistant performing a span-extraction task. You are given an excerpt from a commercial contract and the name of a clause type to locate within it.

Return the exact text of the requested clause, copied verbatim from the excerpt — identical wording and punctuation, with no paraphrasing, summarising, explanation, or added commentary.

The excerpt is one window of a much longer contract and often will not contain the requested clause. If the requested clause does not appear in this excerpt, respond with exactly: Not found.

Output only the extracted clause text, or the exact string `Not found.` — nothing else.

user: Contract excerpt:
"""
Exhibit 10.18 Confidential EXECUTION COPY CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [***], HAS BEEN OMITTED BECAUSE IT IS BOTH NOT MATERIAL AND WOULD BE COMPETITIVELY HARMFUL IF PUBLICLY DISCLOSED. DEVELOPMENT AND OPTION AGREEMENT between HARPOON THERAPEUTICS, INC. and ABBVIE BIOTECHNOLOGY LTD Dated as of November 20, 2019 Source: HARPOON THERAPEUTICS, INC., 10-K, 3/12/2020 TABLE OF CONTENTS ARTICLE 1 DEFINITIONS 1 ARTICLE 2 COLLABORATION MANAGEMENT 18 2.1 Joint Governance Committee. 18 2.2 General Provisions Applicable to the JGC. 19 2.3 Discontinuation of the JGC. 20 2.4 Interactions Between the JGC and Internal Teams. 20 2.5 CMC Working Group. 21 2.6 Working Groups. 21 2.7 Expenses. 21 ARTICLE 3 DEVELOPMENT AND REGULATORY 21 3.1 Initial Development Plan and Activities. 21 3.2 AbbVie Option. 24 3.3 [***]. 25 3.4 Post-Exercise Development Activities. 26 3.5 Supply of Technology for Development Purposes. 27 3.6 Expenses and Invoicing. 27 3.7 Subcontracting. 28 3.8 Regulatory Matters. 28 ARTICLE 4 COMMERCIALIZATION 30 4.1 In General. 30 4.2 Commercialization Diligence. 30 4.3 Booking of Sales; Distribution. 31 4.4 Product Trademarks. 31 4.5 Commercial Supply of Licensed Compounds or Licensed Products. 31 ARTICLE 5 GRANT OF RIGHTS 33 5.1 Grants to AbbVie. 33 5.2 Grants to Harpoon. 34 5.3 Sublicenses. 34 5.4 Distributorships. 34 5.5 Co-Promotion Rights. 34 5.6 Retention of Rights. 34 5.7 Confirmatory Patent License. 35 5.8 Exclusivity with Respect to the Territory. 35 5.9 In-License Agreements. 35 ARTICLE 6 PAYMENTS AND RECORDS 36 6.1 Upfront Payment. 36 6.2 Development and Regulatory Milestones. 36 6.3 First Commercial Sales Milestones. 37 6.4 Sales-Based Milestones. 37 6.5 Royalties. 38 6.6 Royalty Payments and Reports. 39 6.7 Mode of Payment; Offsets. 40 6.8 Withholding Taxes. 40 Source: HARPOON THERAPEUTICS, INC., 10-K, 3/12/2020 6.9 Indirect Taxes. 40 6.10 Interest on Late Payments. 41 6.11 Audit. 41 6.12 Audit Dispute. 41 6.13 Confidentiality. 41 6.14 [***] 41 6.15 No Other Compensation. 42 ARTICLE 7 INTELLECTUAL PROPERTY 42 7.1 Ownership of Intellectual Property. 42 7.2 Maintenance and Prosecution of Patents. 43 7.3 Enforcement of Patents. 45 7.4 Infringement Claims by Third Parties. 48 7.5 Invalidity or Unenforceability Defenses or Actions. 48 7.6 Product Trademarks. 49 7.7 International Nonproprietary Name. 50 7.8 Inventor's Remuneration. 50 7.9 Common Interest. 50 ARTICLE 8 PHARMACOVIGILANCE AND SAFETY 50 8.1 Pharmacovigilance. 50 8.2 Global Safety Database. 50 ARTICLE 9 CONFIDENTIALITY AND NON- DISCLOSURE 51 9.1 Product Information. 51 9.2 Confidentiality Obligations. 51 9.3 Permitted Disclosures. 52 9.4 Use of Name. 53 9.5 Public Announcements. 53 9.6 Publications. 54 9.7 Return of Confidential Information. 54 9.8 Survival. 54 ARTICLE 10 REPRESENTATIONS AND WARRANTIES 55 10.1 Mutual Representations and Warranties. 55 10.2 Additional Representations and Warranties of Harpoon. 55 10.3 Covenants of Harpoon. 58 10.4 Covenants of AbbVie. 58 10.5 DISCLAIMER OF WARRANTIES. 59 ARTICLE 11 INDEMNITY 60 11.1 Indemnification of Harpoon. 60 11.2 Indemnification of AbbVie. 60 11.3 Notice of Claim. 60 11.4 Control of Defense. 61 11.5 Special, Indirect, and Other Losses. 61 11.6 Insurance. 61 ARTICLE 12 TERM AND TERMINATION 62 12.1 Term. 62 - ii - Source: HARPOON THERAPEUTICS, INC., 10-K, 3/12/2020 12.2 Termination for Material Breach. 62 12.3 Additional Termination Rights by AbbVie. 63 12.4 Termination for Insolvency. 63 12.5 Rights in Bankruptcy. 63 12.6 Termination in Entirety. 63 12.7 Reversion of Harpoon Products. 66 12.8 Termination of Terminated Territory. 67 12.9 Remedies. 67 12.10 Accrued Rights; Surviving Obligations. 67 ARTICLE 13 MISCELLANEOUS 68 13.1 Force Majeure. 68 13.2 Change in Control of Harpoon. 68 13.3 Export Control. 69 13.4 Assignment. 69 13.5 Severability. 70 13.6 Governing Law, Jurisdiction and Service. 70 13.7 Dispute Resolution. 70 13.8 Notices. 71 13.9 Entire Agreement; Amendments. 72 13.10 English Language. 72 13.11 Equitable Relief. 72 13.12 Waiver and Non-Exclusion of Remedies. 72 13.13 No Benefit to Third Parties. 72 13.14 Further Assurance. 73 13.15 Relationship of the Parties. 73 13.16 Performance by Affiliates. 73 13.17 Counterparts; Facsimile Execution. 73 13.18 References. 73 13.19 Schedules. 73 13.20 Construction. 73 SCHEDULES Schedule 1.84 Initial Development Plan Schedule 1.99 Licensed Compound Schedule 3.7 Pre-Approved Third Party Providers Schedule 10.2 Disclosure Schedules Schedule 10.2.1 Existing Patents Schedule 13.7.3 Arbitration - iii - Source: HARPOON THERAPEUTICS, INC., 10-K, 3/12/2020 DEVELOPMENT AND OPTION AGREEMENT This Development and Option Agreement (the "Agreement") is made and entered into effective as of November 20, 2019 (the "Effective Date") by and between Harpoon Therapeutics, Inc., a Delaware corporation ("Harpoon"), and AbbVie Biotechnology Ltd, a Bermuda corporation ("AbbVie"). Harpoon and AbbVie are sometimes referred to herein individually as a "Party" and collectively as the "Parties." RECITALS WHEREAS,
"""

Extract the exact clause related to "Irrevocable Or Perpetual License" from the excerpt above.