# EDGAR Filing Document

**Accession Number:** 0001690585
**File Stem:** 0001193125-23-015154
**Filing Date:** 2023-1
**Character Count:** 9959
**Document Hash:** 4a19cd9c26c022da1ef0a915d515e8af
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-23-015154.hdr.sgml**: 20230125

**ACCESSION NUMBER**: 0001193125-23-015154

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 14

**CONFORMED PERIOD OF REPORT**: 20230125

**ITEM INFORMATION**: Regulation FD Disclosure

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20230125

**DATE AS OF CHANGE**: 20230125

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Magenta Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001690585
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **IRS NUMBER:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-38541
- **FILM NUMBER:** 23552579

**BUSINESS ADDRESS:**
- **STREET 1:** 100 TECHNOLOGY SQUARE
- **STREET 2:** 5TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139
- **BUSINESS PHONE:** 857-201-2700

**MAIL ADDRESS:**
- **STREET 1:** 100 TECHNOLOGY SQUARE
- **STREET 2:** 5TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139

?xml version="1.0" encoding="utf-8" ? 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): January 25, 2023

------

## MAGENTA THERAPEUTICS, INC.

#### (Exact name of registrant as specified in its charter)

------

---

| | | |
|:---|:---|:---|
| **Delaware** | **001-38541** | **81-0724163** |
| **(State or other jurisdiction**<br> **of incorporation)** | **(Commission<br>File Number)** | **(I.R.S. Employer<br>Identification No.)** |

---

---

| | |
|:---|:---|
| **100 Technology Square**<br> **Cambridge, Massachusetts** | **02139** |
| **(Address of principal executive offices)** | **(Zip Code)** |

---

#### Registrant's telephone number, including area code: (857) 242-0170

------

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:

---

| | | |
|:---|:---|:---|
| **Title of each class** | **Trading<br>Symbol(s)** | **Name of each exchange**<br> **on which registered** |
| Common Stock, $0.001 Par Value | MGTA | The Nasdaq Global 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. ☐

------

---

| | |
|:---|:---|
| **Item 7.01** | **Regulation FD Disclosure.**  |

---

On January 25, 2023, Magenta Therapeutics, Inc. issued a press release regarding certain clinical updates. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

The information in Item 7.01 of this Current Report on Form 8-K (including Exhibit 99.1) shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

---

| | |
|:---|:---|
| **Item 9.01** | **Financial Statements and Exhibits.**  |

---

(d) Exhibits:

The following exhibit relating to Item 7.01 shall be deemed to be furnished, and not filed:

---

| | |
|:---|:---|
| 99.1 | [Press Release dated January 25, 2023.](d395574dex991.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document). |

---

------

#### 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 hereunto duly authorized.

---

| | |
|:---|:---|
| **MAGENTA THERAPEUTICS, INC.** | **MAGENTA THERAPEUTICS, INC.** |
| Date: | January 25, 2023 |
| By: | /s/ Stephen Mahoney |
|  | Stephen Mahoney |
| Title: | Chief Financial and Operating Officer |

---

## Exhibit 99.1

**Exhibit 99.1**![LOGO](g395574g0126004104930.jpg)

**Magenta Therapeutics Voluntarily Pauses the MGTA-117 Phase 1/2 Dose-Escalation Clinical Trial to Investigate Drug Safety** 

Cambridge, MA – January 25, 2023 – Magenta Therapeutics (Nasdaq: MGTA) today announced that the latest participant dosed at the Cohort 3 level (0.08 mg/kg) in the ongoing MGTA-117 Phase 1/2 Dose-Escalation Clinical Trial in relapsed/refractory acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) experienced a Grade 5 Serious Adverse Event (SAE) (respiratory failure and cardiac arrest resulting in death) deemed to be possibly related to MGTA-117. The known information has been reported to the U.S. Food and Drug Administration (FDA) as a Suspected Unexpected Serious Adverse Reaction (SUSAR). After consultation with the trial's safety Cohort Review Committee and with the highest regard for patient safety, Magenta has voluntarily paused dosing in the clinical trial and is working to evaluate the totality of available data and determine next steps for the development of MGTA-117.

**About Magenta Therapeutics** 

Magenta Therapeutics is a clinical-stage biotechnology company developing medicines designed to bring the curative power of stem cell transplant to more patients with blood cancers, genetic diseases and autoimmune diseases. Magenta is combining leadership in stem cell biology and biotherapeutics development with clinical and regulatory expertise to revolutionize blood and immune reset to allow more patients to take advantage of the curative potential of stem cell transplant and potentially improve eligibility for future gene therapies.

Magenta is based in Cambridge, Mass. For more information, please visit www.magentatx.com.

Follow Magenta on Twitter: @magentatx.

**Forward-Looking Statements** 

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995, as amended. These statements include, without limitation, implied and express statements relating to: Magenta working to evaluate the totality of available data and determine next steps for the development of MGTA-117.

------

Words such as "anticipate," "believe," "continue," "could," "designed," "endeavor," "estimate," "expect," "intend," "may," "might," "plan," "potential," "predict," "project," "seek," "should," "target," "preliminary," "will," "would" and similar expressions are intended to identify forward-looking statements. The express or implied forward-looking statements included in this press release are only predictions and are subject to a number of risks, uncertainties and assumptions, including, without limitation: volatility and uncertainty in the capital markets for biotechnology companies; uncertainties inherent in preclinical and clinical trials and in the availability and timing of data from ongoing and planned clinical and preclinical trials; the ability to initiate, enroll, conduct or complete ongoing and planned preclinical and clinical trials; vulnerability and/or fragility of, and the presence of underlying disorders in, the patient population for the clinical trials of Magenta's product candidates, including the MGTA-117 Phase 1/2 clinical trial in patients with relapsed/refractory AML and MDS; that preliminary data from Magenta's clinical trials may change materially following a more comprehensive review of the data; the delay of any current or planned preclinical or clinical trials, or the delay in development of Magenta's product candidates; whether results from preclinical or earlier clinical trials will be predictive of the results of future trials; interactions with regulatory agencies such as the U.S. Food and Drug Administration; the expected timing of submissions for regulatory approval to conduct or continue trials or to market products; Magenta's ability to successfully demonstrate the safety and efficacy of its product candidates; whether Magenta's cash resources will be sufficient to fund Magenta's foreseeable and unforeseeable operating expenses and capital expenditure requirements; and risks, uncertainties and assumptions regarding the impact of the continuing COVID-19 pandemic on Magenta's business, operations, preclinical activities, clinical trials, strategy, goals and anticipated timelines. These and other risks are described in additional detail in Magenta's Quarterly Report on Form 10-Q for the quarter ended September 30, 2022, and its other filings made with the Securities and Exchange Commission from time to time. Any forward-looking statements contained in this press release represent Magenta's views only as of today and should not be relied upon as representing its views as of any subsequent date. Magenta explicitly disclaims any obligation to update any forward-looking statements, except to the extent required by law.