ViroLogic's eTag System Demonstrates Potential Ability to Better Select Breast Cancer Patients for Therapy With Herceptin

ViroLogic's eTag System Demonstrates Potential Ability to Better
Select Breast Cancer Patients for Therapy With Herceptin
-Abstract #553- 


ORLANDO, Fla., May 17  /PRNewswire-FirstCall/ -- ViroLogic, Inc., (NASDAQ:VLGC)
announced today the presentation of clinical data demonstrating the ability of
the company's eTag(TM) assays to accurately predict treatment response for
patients with breast cancer who receive Herceptin(R) (trastuzumab).  The
presentation took place at the 2005 American Society of Clinical Oncology
(ASCO) Annual Meeting being held this week at the Orange County Convention
Center in Orlando, FL.

ViroLogic has developed a set of eTag assays that enables broader analysis of
the human epidermal growth factor receptor (HER) family than just HER2/neu, the
target for the antibody drug Herceptin, and uniquely permits measurement of
"activated" HER receptors in fixed patient tumor samples.  Breast cancer
patients who over-express the HER2/neu protein, or who have excess copies of
the HER2/neu gene, are typically treated with Herceptin. However, approximately
60% of patients that test positive for HER2/neu by these methods and are
treated with Herceptin do not respond to therapy, suggesting that other
mechanisms are likely driving tumor cell growth and contributing to disease
progression in these patients.

"Our data indicate that the eTag assays, which are directed to activated HER
receptor family targets, may more accurately predict response in patients with
breast cancer than current methods that look at gene amplification and protein
levels of just HER2," said Sharat Singh, Ph.D., ViroLogic's Chief Technical
Officer, Oncology, and co-author of the study.  "A larger study of
Herceptin-treated patients is being undertaken to further assess the clinical
utility of eTag assays in the selection of breast cancer patients for
receptor-targeted therapies."

Researchers at ViroLogic used eTag assays to analyze breast tissue biopsies
from 30 patients treated with Herceptin, including 13 samples from an earlier
study with the Tokyo Metropolitan Institute of Medical Science (Rinshoken), to
determine total HER receptor family expression, HER homo- and heterodimer
levels (indicative of activated receptor) and the phosphorylation states of the
HER receptors on formalin-fixed, paraffin-embedded tissue sections. The data
from these studies were then used to correlate with patient response to
Herceptin.

Patient samples were analyzed blinded, and the patients were divided into two
groups based on their HER receptor activation level.  In the first group were
patients who exhibited high levels of HER3-containing dimers, and who were
predicted to have progressive disease because Herceptin does not affect these
molecules.  In the second group were patients who showed high levels of
HER2/neu homodimers only, or high levels of HER2/neu homodimers and low to
moderate levels of Her3-containing heterodimers, who were predicted to respond
(complete response/partial response/stable disease) to Herceptin treatment. The
difference between these two groups based on the eTag assay-predicted clinical
response to Herceptin treatment was highly statistically significant, reaching
a p-value of 0.0017.  Sensitivity was 90% and specificity was 70%.

"These expanded study results are consistent with our early findings from the
Rinshoken study, where medium-to-high levels of Her2 homodimers when coupled
with high levels of Her3 heterodimers, as measured by eTag assays, had a
negative correlation with response," continued Dr. Singh.

About the eTag System

ViroLogic's eTag assays enable detailed analysis of protein drug targets and
signaling pathways in cancer cells, including samples that are formalin-fixed,
paraffin-embedded, which is the standard format in most pathology labs.  The
assays can provide information on a drug's mechanism of action, selectivity and
potency in a biological setting in pre-clinical research, and enable enrichment
or selection of clinical trial populations later in a drug's development.  In
addition, ViroLogic believes these assays may ultimately be used to help
physicians better determine whether certain therapies are more appropriate for
individual cancer patients, and whether to combine therapies with different
mechanisms or properties.  The first commercially available activated receptor
test panel based on eTag technology, focused on the EGFR/HER receptor family,
is planned to be introduced in 2006.

About ViroLogic

ViroLogic is a biotechnology company advancing individualized medicine by
discovering, developing and marketing innovative products to guide and improve
treatment of serious infectious diseases and cancer.  The Company's products
are designed to help doctors optimize treatment regimens for their patients
that lead to better outcomes and reduced costs.  The Company's technology is
also being used by numerous biopharmaceutical companies to develop new and
improved antiviral therapeutics and vaccines as well as targeted cancer
therapeutics.  More information about the Company and its technology can be
found on its web site at http://www.virologic.com/.

FORWARD LOOKING STATEMENTS

Certain statements in this press release are forward-looking, including
statements regarding the trend toward individualized medicine and the results
of yet-to-be completed clinical studies related to the effectiveness of our
eTag assays as predictive tools for targeted cancer therapies. These
forward-looking statements are subject to risks and uncertainties and other
factors, which may cause actual results to differ materially from the
anticipated results or other expectations expressed in such forward-looking
statements. These risks and uncertainties include, but are not limited to,
risks and uncertainties relating to the development of future products; the
performance of our products; our ability to successfully conduct clinical
studies and the results obtained from those studies; whether larger
confirmatory clinical studies will confirm the results of initial studies;
whether larger studies involving tumor samples will yield favorable results
regarding the predictive capability of eTag assays for responsiveness to
Herceptin; our ability to establish reliable, high-volume operations at
commercially reasonable costs; our ability to introduce a product commercially
in 2006; our ability to successfully integrate the operations of ACLARA into
our operations; competition from larger more established diagnostic providers;
actual market acceptance of our products and adoption of our technological
approach and products by pharmaceutical and biotechnology companies; our
estimate of the size of our markets; our estimates of the level of demand for
our products; the timing and ultimate size of pharmaceutical company clinical
trials; whether payors will authorize reimbursement for our products; whether
the FDA or any other agency will seek to regulate ViroLogic's in house clinical
laboratory testing; our ability to comply with FDA regulations in order to
establish and maintain diagnostic kit manufacturing operations; whether we will
encounter problems or delays in establishing and validating eTag assays within
our clinical laboratory; whether we will encounter problems or delays in
automating our processes or expanding our capacity; whether the intellectual
property underlying the Company's technology is adequate; whether we may be
deemed to infringe on the intellectual property of others and whether licenses
to third party technology will be available; whether ViroLogic is able to build
brand loyalty and expand revenues; the potential impact of any payments under
the CVRs on our common stock and capital resources; and whether ViroLogic will
be able to raise sufficient capital when required. For a discussion of other
factors that may cause ViroLogic's actual events to differ from those
projected, please refer to the Company's most recent annual report on Form 10-K
and quarterly reports on Form 10-Q, as well as other subsequent filings with
the Securities and Exchange Commission.  We do not undertake, and specifically
disclaim any obligation, to revise any forward looking statements to reflect
the occurrence of anticipated or unanticipated events or circumstances after
the date of such statements.

NOTE:  eTag is a trademark of ViroLogic, Inc. Herceptin(R) is a registered
trademark of Genentech. 

DATASOURCE: ViroLogic, Inc.



CONTACT:  Alfred Merriweather, Vice President and CFO of ViroLogic,

[phone], or Carolyn Bumgardner Wang of WeissComm Partners,

[phone], or , for ViroLogic



Web site:  http://www.virologic.com/

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