* Says patient dies from blood clot in lungs
* Working with FDA on next steps on drug development
* SunTrust analysts still see chance of success for drug
* Shares fall as much as 63 pct (Adds details, analyst comments; updates shares)
By Vidya L Nathan
Dec 2 (Reuters) - A second patient died in a late-stage trial of Zafgen Inc’s experimental obesity treatment, highlighting safety concerns associated with drugs that aim to treat a condition that affects one in three Americans.
Zafgen’s shares tumbled as much as 63 percent to a record low of $5.93 on Wednesday morning as is was unclear if the company would continue testing the drug.
The company said a patient receiving the drug, beloranib, died from a blockage in an artery in the lung.
Zafgen, which is testing beloranib for a rare genetic eating disorder called Prader-Willi syndrome, expects to report results from the study in the first quarter. The company declined to comment beyond Wednesday’s statement.
SunTrust Robinson Humphrey analysts said they still see more than a 40 percent chance of success for beloranib as it is not known if the blood clot was caused by the drug.
The company said in October a patient had died in the trial, but the cause of death was unknown. Following the disclosure the FDA placed the trial under a partial clinical hold, citing previously reported blood clotting in ongoing and completed studies.
The two deaths in the 108-patients-strong study come after clean smaller studies on the drug, where the most severe side-effect seen was bruising where the patients were given the injection.
Zafgen is also developing the drug to treat other weight-related disorders such as severe and complicated obesity, and obesity that results from damage to a part of the brain.
Obesity treatments have been plagued by safety concerns, particularly related to heart risk and birth defects, and several have been taken off the market.
The U.S. Food and Drug Administration (FDA) approved drugs made by Vivus Inc, Orexigen Therapeutics Inc and Arena Pharmaceuticals Inc in the recent past, but has asked for additional studies to check for safety of these drugs.
The treatments suppress appetite by tinkering with nerve signals, tricking the brain into thinking that the stomach is full.
Zafgen’s beloranib takes a different approach. The drug is designed to make the body produce less fat and burn off the excess as fuel.
The drug works by blocking an enzyme called methionine aminopeptidase 2, which plays a key role in the production and use of fatty acids.
Zafgen said on Wednesday that it is discussing with the FDA on the next steps for beloranib, its lead drug candidate. (Reporting by Vidya L Nathan in Bengaluru; Editing by Saumyadeb Chakrabarty)