A UK clinical trial testing an antibody treatment for coronavirus - including on patients in Bradford - will continue “as planned” after a US study stopped enrolling the sickest patients in its trials of the drug.

Regeneron Pharmaceuticals said independent monitors had recommended pausing enrolment of the most severely-ill patients – those who need intense oxygen treatment or breathing machines – to the REGN-COV2 trial because of a potential safety problem and unfavourable balance of risks and benefits.

The study can continue to test the two-antibody drug combination in hospital patients who need little or no extra oxygen, the monitors said.

Other studies in mild or moderately ill people are also continuing.

The co-leads of Oxford University’s national Recovery trial - which has recruited around 150 people from Bradford - said experimental antibody drug REGN-COV2 was part of their clinical trial to identify treatments for people in hospital with suspected or confirmed Covid-19.

But Professor Peter Horby and Professor Martin Landray said the Recovery trial will continue as planned.

In a joint statement on Friday, they added: “Today Regeneron have issued a statement announcing a pause in recruitment of Covid-19 patients with high oxygen requirements to one of their trials of the REGN-COV2 antibody cocktail.

“We note that this is a hold pending collection and analysis of further data, and that enrolment and randomisation of other patients with Covid-19 to this and other studies of the drug continues.

“Since REGN-COV2 is being studied in the Recovery trial, we have today discussed this announcement with Regeneron, with the UK Medicines and Healthcare products Regulatory Agency (MHRA), and with the chair of the Recovery independent data monitoring committee.

“The independent data monitoring committee will review the latest data from the ongoing Recovery trial on Thursday November 5. In the meantime, the Recovery trial will continue as planned.”

US President Donald Trump was given the antibody treatment REGN-COV2 on compassionate grounds by its US manufacturer Regeneron.

REGN-COV2 is made up of two monoclonal antibodies (REGN10933 and REGN10987), which are man-made and act like human antibodies in the immune system.

The cocktail of drugs targets two components in the spike protein of the Covid-19 virus, with the aim of interrupting its ability to infect cells.

REGN-COV2 is currently being trialled globally, including in UK hospitals, where at least 2,000 patients will receive it.

The Recovery study, co-ordinated by the University of Oxford, will assess the impact of giving patients the drug alongside usual standard care, to see if it lessens the severity of Covid-19 and can reduce deaths.

Regeneron said it had received a recommendation from the independent data monitoring committee (IDMC) for the REGN-COV2 trials to put further the enrolment of patients requiring high-flow oxygen or mechanical ventilation on hold.

It added that this was based on “a potential safety signal and an unfavourable risk/benefit profile”.

But the IDMC also recommended continuing enrolment of hospital patients who need little or no extra oxygen and continuing the outpatient trial, Regeneron added.

In a statement it added: “Regeneron remains blinded to the data and is implementing the IDMC recommendations.

“Regeneron is also informing the US Food and Drug Administration, which is currently evaluating REGN-COV2 for a potential emergency use authorization in mild-to-moderate outpatients at high risk for poor outcomes.

“Regeneron is also sharing the recommendation with the independent committee monitoring the Recovery trial in the UK, which is evaluating REGN-COV2 in hospitalised patients.”