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Cellectis (NASDAQ: CLLS) showcases TALEM epigenetic gene-silencing platform

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Form Type
6-K

Rhea-AI Filing Summary

Cellectis filed a Form 6-K sharing a press release on new epigenetic editing research presented at the ASGCT annual meeting. The work uses TALE-based epigenetic modulators (TALEM) to turn genes off without cutting or permanently changing DNA, which the company describes as a potentially safer genome-editing approach.

Cellectis developed a high-throughput screening system to rapidly assemble and test hundreds of TALEM constructs and identified combinations that strongly control specific genes. In hepatocytes and T-cells, the method achieved more than 90% sustained reduction in target gene activity, supporting Cellectis’ broader gene-editing and allogeneic CAR T therapy platform.

Positive

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ASGCT meeting dates May 11–15 American Society of Gene and Cell Therapy annual meeting in Boston
Poster presentation time May 13, 2026, 5 pm ET Scheduled time for Cellectis TALEM poster presentation
Gene activity reduction >90% reduction Knock-down of target genes in hepatocytes and T-cells using TALEM
Annual report year referenced Year ended December 31, 2025 Period referenced for risk-factor disclosures in Cellectis reports
epigenetic editing technical
"a TALE-based epigenetic editing approach, that does not cut or permanently modify the DNA sequence"
Epigenetic editing is a method that changes chemical tags on DNA or its packaging to turn specific genes on or off without altering the underlying genetic code. Think of it like adding or removing sticky notes on an instruction manual to change which instructions are read. For investors, it matters because this approach can enable precise, potentially reversible treatments for diseases with different safety and regulatory profiles than permanent gene edits, affecting clinical value and commercial potential.
Transcription activator-like effector-based epigenetic modulators technical
"Transcription activator-like effector-based epigenetic modulators (TALEM) are engineered fusion proteins"
TALEM technical
"Cellectis developed a high-throughput screening system capable of rapidly assembling and testing hundreds of these TALEM"
CAR T immunotherapies technical
"The company utilizes an allogeneic approach for CAR T immunotherapies in oncology"
allogeneic approach technical
"The company utilizes an allogeneic approach for CAR T immunotherapies in oncology"
forward-looking statements regulatory
"This press release contains “forward-looking” statements within the meaning of applicable securities laws"
Forward-looking statements are predictions or plans that companies share about what they expect to happen in the future, like estimating sales or profits. They matter because they help investors understand a company's outlook, but since they are based on guesses and assumptions, they can sometimes be wrong.
 

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

Date of Report: April 27, 2026

Commission File Number: 001-36891

Cellectis S.A.
(Exact Name of registrant as specified in its charter)

8, rue de la Croix Jarry
75013 Paris, France
+33 1 81 69 16 00

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.
Form 20-F [ X ]      Form 40-F [   ]

 

 


EXHIBIT INDEX

Exhibit Title
   
99.1 Press release, dated April 27, 2026

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.

      Cellectis S.A.    
  (Registrant)
   
  
Date: April 27, 2026     /s/ André Choulika    
  André Choulika
  Chief Executive Officer
  

EXHIBIT 99.1

Cellectis Presents Epigenetic Editing Platform to Turn Genes Off Without Altering DNA at the ASGCT Annual Meeting

NEW YORK, April 27, 2026 (GLOBE NEWSWIRE) -- Cellectis (the “Company”) (Euronext Growth: ALCLS - NASDAQ: CLLS), a clinical-stage biotechnology company using its pioneering gene editing platform to develop life-saving cell and gene therapies, today presents new research on a TALE-based epigenetic editing approach, that does not cut or permanently modify the DNA sequence, making it a potentially safer alternative for genome editing, at the American Society of Gene and Cell Therapy (ASGCT) annual meeting, that will be held on May 11-15, in Boston (MA).

The data will be presented in a poster:

Title: TALE-based epigenetic modulators show sustained knock-down of target genes in T-cells and HEPG2 via a high-throughput multiplex screening platform

Transcription activator-like effector-based epigenetic modulators (TALEM) are engineered fusion proteins consisting of a TALE DNA-binding domain with functional domains that mediate epigenetic modifications. These proteins can be precisely guided to a target location in the genome to switch genes on or off through a process known as epigenetic editing.

Unlike traditional gene editing tools, this approach does not induce DNA breaks and DNA sequence modifications, making it a potentially safer alternative for genome editing.

In this work, Cellectis developed a high-throughput screening system capable of rapidly assembling and testing hundreds of these TALEM, identifying which combinations are most effective at regulating a given gene.

The results: 

This strategy was used for two distinct genes: one highly expressed in hepatocytes (active in liver cells) and another implicated in T-cell dysfunction and exhaustion, a key challenge in cancer immunotherapy. In both cases, the approach achieved >90% reduction in gene activity, which remained stable throughout the study.

“We are excited to present these results at ASGCT, which demonstrate Cellectis’ ability to apply its gene editing platform into the emerging field of epigenetic editing” said Louisa Mayer, Ph.D., Scientist II and Supervisor - Innovation & Gene Editing at Cellectis. “This work shows our ability to design and identify highly potent epigenetic editors across different cell types, thereby enriching our gene‑editing toolbox.”

The abstract is published on the ASGCT website. The poster will be available on Cellectis’ website on the presentation day, Wednesday May 13, 2026 at 5 pm ET.

About Cellectis
Cellectis is a clinical-stage biotechnology company using its pioneering gene-editing platform to develop life-saving cell and gene therapies. The company utilizes an allogeneic approach for CAR T immunotherapies in oncology, pioneering the concept of off-the-shelf and ready-to-use gene-edited CAR T-cells to treat cancer patients, and a platform to develop gene therapies in other therapeutic indications. With its in-house manufacturing capabilities, Cellectis is one of the few end-to-end gene editing companies that controls the cell and gene therapy value chain from start to finish.

Cellectis’ headquarters are in Paris, France, with locations in New York and Raleigh, NC. Cellectis is listed on the Nasdaq Global Market (ticker: CLLS) and on Euronext Growth (ticker: ALCLS). To find out more, visit www.cellectis.com and follow Cellectis on LinkedIn and X.

Cautionary Statement 

This press release contains “forward-looking” statements within the meaning of applicable securities laws, including the Private Securities Litigation Reform Act of 1995. Forward-looking statements may be identified by words such as “can,” or “potentially,” or the negative of these and similar expressions. These forward-looking statements are based on our management’s current expectations and assumptions and on information currently available to management. Forward-looking statements include statements about the potential of our innovation programs. These forward-looking statements are subject to significant risks and uncertainties, including those described in our Annual Report on Form 20-F as amended and in our annual financial report (including the management report) for the year ended December 31, 2025 and subsequent filings Cellectis makes with the Securities Exchange Commission from time to time, which are available on the SEC’s website at www.sec.gov, as well as other known and unknown risks and uncertainties may adversely affect such forward-looking statements and cause our actual results, performance or achievements to be materially different from those expressed or implied by the forward-looking statements. Except as required by law, we assume no obligation to update these forward-looking statements publicly, or to update the reasons why actual results could differ materially from those anticipated in the forward-looking statements, even if new information becomes available in the future.

For further information on Cellectis, please contact:

Media contacts:
Pascalyne Wilson, Director, Communications, + 33 (0)7 76 99 14 33, media@cellectis.com         

Patricia Sosa Navarro, Chief of Staff to the CEO, +33 (0)7 76 77 46 93

Investor Relations contact:
Arthur Stril, Chief Financial Officer & Chief Business Officer, investors@cellectis.com

Attachment

  • PRESS RELEASE_ ASGCT (https://ml.globenewswire.com/Resource/Download/3c0eb218-da31-4056-9a5f-8df548e7aa08)

FAQ

What did Cellectis (CLLS) announce in its latest Form 6-K?

Cellectis reported new research on a TALE-based epigenetic editing platform that turns genes off without cutting DNA. The data, presented at the ASGCT meeting, showed strong, durable gene knock-down in liver and T-cells using engineered TALEM fusion proteins.

How does Cellectis’ TALEM epigenetic editing approach work?

Cellectis’ TALEM proteins combine a TALE DNA-binding domain with epigenetic modifier domains to switch genes on or off. They target specific genomic locations without inducing DNA breaks, offering a potentially safer way to control gene activity compared with traditional gene-editing tools.

What results did Cellectis (CLLS) report from its TALEM platform?

The company reported more than 90% reduction in activity of two target genes using TALEM constructs. This knock-down remained stable over the study period, in both hepatocytes and T-cells, supporting the platform’s potential for robust, sustained gene regulation.

Why is Cellectis’ epigenetic editing research important for its pipeline?

The research expands Cellectis’ gene-editing toolbox with non-cutting epigenetic editors that may be safer for therapeutic use. It complements the company’s allogeneic CAR T and gene therapy programs by enabling precise, durable control of gene expression across different cell types.

Where and when is Cellectis presenting these TALEM data?

Cellectis is presenting the TALEM epigenetic editing data in a poster at the ASGCT annual meeting held May 11–15 in Boston. The poster is scheduled for Wednesday, May 13, 2026 at 5 pm ET and will also be available on Cellectis’ website.

What type of company is Cellectis (CLLS)?

Cellectis is a clinical-stage biotechnology company focused on gene editing for cell and gene therapies. It uses an allogeneic, off-the-shelf CAR T approach in oncology and maintains in-house manufacturing, with shares listed on Nasdaq and Euronext Growth under tickers CLLS and ALCLS.

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