# EDGAR Filing Document

**Accession Number:** 0001501989
**File Stem:** 0001193125-26-255467
**Filing Date:** 2026-6
**Character Count:** 6117
**Document Hash:** fa9bf092d347b617e3f60303506b1957
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-255467.hdr.sgml**: 20260603

**ACCESSION NUMBER**: 0001193125-26-255467

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 11

**CONFORMED PERIOD OF REPORT**: 20260529

**ITEM INFORMATION**: Entry into a Material Definitive Agreement

**FILED AS OF DATE**: 20260603

**DATE AS OF CHANGE**: 20260603

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** CytomX Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001501989
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 273521219
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-37587
- **FILM NUMBER:** 261060789

**BUSINESS ADDRESS:**
- **STREET 1:** 151 OYSTER POINT BLVD.
- **STREET 2:** SUITE 400
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080
- **BUSINESS PHONE:** 650.515.3185

**MAIL ADDRESS:**
- **STREET 1:** 151 OYSTER POINT BLVD.
- **STREET 2:** SUITE 400
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080

?xml version='1.0' encoding='ASCII'? 8-K

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### WASHINGTON, D.C. 20549

### FORM 8-K

#### CURRENT REPORT

#### Pursuant to Section 13 or 15(d)

#### of the Securities Exchange Act of 1934

#### Date of Report (Date of earliest event reported): May 29, 2026

## CytomX Therapeutics, Inc.

#### (Exact name of Registrant as Specified in Its Charter)

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| | | |
|:---|:---|:---|
| **Delaware** | **001-37587** | **27-3521219** |
| **(State or Other Jurisdiction<br>of Incorporation)** | **(Commission**<br> **File Number)** | **(IRS Employer<br>Identification No.)** |

---

---

| | |
|:---|:---|
| **151 Oyster Point Blvd** |  |
| **Suite 400** |  |
| **South San Francisco, California** | **94080** |
| **(Address of Principal Executive Offices)** | **(Zip Code)** |

---

#### Registrant's Telephone Number, Including Area Code: 650-515-3185

#### Not Applicable

#### (Former Name or Former Address, if Changed Since Last Report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

#### Securities registered pursuant to Section 12(b) of the Act:

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| | | |
|:---|:---|:---|
| **<br>Title of each class** | **Trading<br>Symbol(s)** | **Name of each exchange<br>on which registered** |
| Common Stock, $0.00001 par value per share | CTMX | Nasdaq Global Select Market |

---

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

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| | |
|:---|:---|
| **Item 1.01** | **Entry into a Material Definitive Agreement.**  |

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CytomX Therapeutics, Inc. (the "Company") previously entered into that certain Collaboration and License Agreement, effective November 16, 2022 (as amended, the "Agreement"), with Regeneron Pharmaceuticals, Inc. ("Regeneron"), providing for the collaboration on the creation of conditionally-activated investigational bispecific cancer therapies utilizing the Company's Probody<sup>®</sup> therapeutic platform and Regeneron's Veloci-Bi<sup>®</sup> bispecific antibody development platform. On May 29, 2026, the Company and Regeneron entered into Amendment No. 4 to the Agreement ("Amendment No. 4"), effective May 31, 2026, pursuant to which the parties agreed to (i) extend the program selection period within which Regeneron may nominate additional collaboration programs and (ii) provide for the addition of up to eight additional collaboration programs to the Agreement, of which Regeneron has nominated the first two as described below, and the remaining six of which are subject to Regeneron's exercise of its nomination option and payment of certain per-program nomination fees. Total potential target nomination payments and preclinical, clinical, regulatory and commercial milestones covered under the scope of the Agreement are up to approximately $4 billion. The royalty obligations under the Agreement, including the tiered royalty rates on global net sales of licensed products previously disclosed by the Company, are not modified by Amendment No. 4.

Additionally, in connection with Amendment No. 4, Regeneron nominated the first two additional collaboration programs under the Agreement, entitling the Company to receive aggregate target nomination payments of $37.0 million.

The foregoing summary of the material terms of Amendment No. 4 is qualified in its entirety by the full text thereof, a copy of which will be filed as an exhibit to the Company's Quarterly Report on Form 10-Q for the quarterly period ending June 30, 2026. The Company intends to omit certain confidential portions of Amendment No. 4.

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#### SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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| | | |
|:---|:---|:---|
|  | **CYTOMX THERAPEUTICS, INC.** | **CYTOMX THERAPEUTICS, INC.** |
| Date: June 3, 2026 | By: | /s/ Leslie J.B. Robbins |
|  |  | Leslie J.B. Robbins <br>*Senior Vice President, Intellectual Property* |

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