INmune Bio has some explaining to do to the FDA before the company can continue with its trial of XPro, an investigational new drug intended to treat Alzheimer’s.

While the FDA has yet to make a statement about it or send the official hold letter to the company, INmune announced that the agency requested additional information on the Chemistry Manufacturing Controls of the new drug, XPro1595.

Xpro1595 is a next-generation tumour necrosis factor (TNF) inhibitor that acts differently than currently available TNF inhibitors in that it neutralizes soluble TNF (sTNF), without affecting trans-membrane TNF or other receptors. The drug works could alleviate Alzheimer’s symptoms by decreasing neuroinflammation and improving cognitive function.

The FDA said they will provide an official letter — placing the company’s IND for its phase 2 U.S. trial on clinical hold — to INmune in the next month or so. The company also announced that the phase 2 trial of XPro remains open in Australia and continues to enrol patients.