THIOMAB Antibiotic Conjugate (TAC): A Novel Platform for Invasive Staphylococcus aureus Infection

Embargoed Until: Friday 9/18/2015 12:00 pm PST

Author: Chenguang Zhou

Control number: 694


Resistance to antibiotics is a growing worldwide public health threat and our ability to manage infections caused by resistant bacteria is waning.  One of the most common infections globally is caused by Staphylococcus aureus (S. aureus or “staph”).  In many cases S. aureus has acquired resistance to currently approved antibiotics including methicillin, these bacteria are known as Methicillin-resistant Staphylococcus aureus or MRSA. Alarmingly, in the United States, MRSA infections lead to 278,000 hospitalizations and 11,285[1] deaths each year.

During an infection the cells in the human immune system engulf and destroy the bacteria. However, it’s been known for many years that during a S. aureus infection of the blood, while the vast majority bacteria are destroyed, a small proportion remain alive in human immune cells (Garzoni and Kelley, 2008).  These “intracellular” bacteria may be able to avoid being killed by antibiotics currently used to treat S. aureus infections. These bacteria hiding within an immune cell may be responsible for subsequent infections that are not cured despite treatment with antibiotics.

Genentech scientists are developing a novel platform, called THIOMAB™ Antibiotic Conjugate (TAC), to fight resistant infections. The TAC compound consists of an antibody specifically designed to bind to the surface of bacteria. To that antibody, we have linked a new antibiotic intended to kill S. aureus. Once the TAC compound binds to the bacteria, both will be taken up by human immune cells, where the antibiotic is then released and can kill bacteria within the very cells where they used to hide. Genentech has successfully used a similar approach linking chemotherapy to antibodies to directly target cancer cells. 

At the ICAAC 2015 meeting, Genentech is reporting preclinical results from studies performed to understand what happens to the TAC once in the bloodstream. These studies showed that after mice are given a single dose of the TAC compound, the antibiotic stays in circulation for weeks (as opposed to 6-24 hours which is the case for most antibiotics) and is able to kill S. aureus, including MRSA, for up to two weeks.  These findings suggest that the TAC compound may provide a new way to kill S. aureus bacteria.


For more information, please call Genentech’s media line at 650-467-6800.

[1] CDC Report: Antibiotic Resistance Threats in the United States, 2013