One of the Chinese scientific community’s most heralded contributions to the field of genetic engineering received an “Editorial Expression of Concern” — often a precursor to a full retraction — from the scientific journal Nature Biotechnology on Monday.

Han Chunyu and his four co-authors from the little-known Hebei University of Science and Technology (HEBUST) reported a breakthrough in gene editing that would allow scientists to more efficiently boost the human body’s resistance to diseases like cancer. Such a precise editing technique could also potentially be used to create designer babies.

Before Han’s research was published, CRISPR-Cas9 was the global standard in gene editing, but the Cas9 protein doesn’t always target the correct genetic sequences. Han and his colleagues, however, had successfully used another enzyme — NgAgo — to edit sequences more accurately, they claimed in their paper, published in Nature Biotechnology on May 2.

Following the Chinese team’s revelations, researchers around the world began attempting to replicate the groundbreaking experiment. They soon found, however, that no matter how many times they tried, they could not achieve the same outcome. Gaetan Burgio, a geneticist at the Australian National University, drew attention to the discrepancy when he described his own failure to reproduce Han’s results in a July blog post, sparking outcry from an increasingly skeptical international scientific community.

Han, who was already being lauded as a Nobel Prize contender in China, and his university soon found themselves embroiled in controversy. But rather than address the accusations of negligence (at best) and fraud (at worst) in an open and transparent manner, Han and HEBUST went silent, with the latter saying only that it would provide proof of the team’s findings before September. The month came and went with no comment from the university, although Han has since been elected vice president of the provincial Association for Science and Technology and received a grant of more than 224 million yuan ($33.3 million) — far more than the university’s annual revenue of 86 million yuan — to set up a gene editing research center at HEBUST.

On Monday, three research teams from Germany, South Korea, and the U.S. published their own joint paper in Nature Biotechnology refuting the results of Han and his colleagues. The scientists, led by Toni Cathomen of the University of Freiburg, followed the exact experimental setup outlined in Han’s paper but did not obtain statistically significant results. Their paper stated: “Despite various attempts to optimize NgAgo-mediated genome editing of the reported cell lines, no evidence of successful editing […] was detected.”

Along with the Cathomen group’s paper, Nature Biotechnology published an Editorial Expression of Concern “regarding the reproducibility of the original results.” After contacting the Chinese authors, the journal reported that Han and another author “agree with the editorial expression of concern,” while the remaining three authors “do not feel that it is appropriate at this time.”

Nature Biotechnology said in the statement that it would continue to work with the authors of the original paper and provide them with an opportunity to reproduce their results, imposing a deadline of January 2017. “An update will be provided to the community at that time,” the statement concluded.

(Header image: Corbis Documentary/VCG)