Han Chunyu, an associate professor at Hebei University of Science and Technology (HEBUST), and his colleagues on Thursday retracted their controversial thesis on a new gene-editing technique from Nature Biotechnology, an international journal under the Nature brand of publications.

The withdrawal is because of “the continued inability of the research community to replicate the key results” using the same protocol, according to a statement from Han and his team, published Thursday in the journal. While the team retracted the thesis to “maintain the integrity of the scientific record,” they said they would continue to investigate the reasons why the findings could not be reproduced and provide a solid methodology for doing so.

An editorial from Nature Biotechnology published the same day called the retraction “the best course of action,” and a “testament” to the time and effort invested by scientists around the world to verify the claimed results of the team.

Han published a paper in Nature Biotechnology last May on human genome editing using an enzyme called NgAgo, a technology potentially applicable to curing cancer. While claiming NgAgo could locate and cut the gene sequences more accurately than CRISPR-Cas9, a dominant technology in the field of genome editing, the findings were met with enthusiasm by scientists both in China and abroad.

But this initial excitement soon gave way to skepticism, as dozens of peers in the scientific community were unable to reproduce the same results. Last November, 20 scientists from the United States and China jointly published a letter in Protein & Cell, a Chinese journal on biological science, announcing zero successful cases in their experiments with NgAgo genome editing. They urged the original authors to clarify the method used in their study and provide the details needed to replicate the results.

Two weeks later, Nature Biotechnology followed up by publishing research results from three research groups in Germany, the U.S., and South Korea who had also tried to reproduce Han’s work but had failed to observe signs of gene mutation induced by NgAgo. Together with the research results, the journal issued an “Editorial Expression of Concern,” a common step before a full retraction.

Han later submitted additional research data to Nature Biotechnology. In a January response to The Paper, Sixth Tone’s sister publication, the journal said it was exploring the newly available data prior to taking further action. Thursday’s editorial explained that Han and several independent groups had claimed to have reproduced the results successfully, although the data failed to satisfy the journal’s publication standards.

Han has received extensive attention from the scientific community and the media since publishing his research. He received multiple awards both for himself and his university, including 224 million yuan ($33.3 million) from the Hebei provincial government for establishing a gene-editing research center at HEBUST, and a promotion to the position of vice president of Hebei’s Association for Science and Technology, a government-sponsored science league.

Han remained largely silent despite repeated calls for clarification from fellow scientists and the media. In the rare case that he did respond, as he did to state-owned broadcaster China Central Television, he maintained that his research was replicable, and that an important reason for failure could be cell contamination. Sixth Tone could not reach Han for comment.

HEBUST published a notice on its website Thursday morning saying they will begin a peer review of Han’s research results, and that Han’s team has agreed to the school’s arrangement for a third-party lab to further examine the initial findings.

This is not the first time that a Chinese scholar has retracted a thesis from an international journal. Earlier this year, 107 papers, mostly authored by Chinese academics, were retracted from Tumor Biology, an international scientific journal, because the articles’ peer reviews were discovered to be fake.

“Publication of the NgAgo paper was not the end of the scientific process, it was the start,” Nature Biotechnology wrote in the Thursday editorial. While acknowledging the time-consuming yet unrewarded work of scientists in replication studies, it stated that in the case of the research by Han and his colleagues, “the time has come and the data has spoken.”

Editor: Colum Murphy.

This article has been updated to include a response from Hebei University of Science and Technology.

(Header image: A portrait of Han Chunyu is displayed on a screen in Shanghai, Aug. 2, 2017. Wu Huiyuan/Sixth Tone)