Amsterdam Molecular Therapeutics Presents Data Supporting Role of Chylomicron Clearance as Marker for Glybera(R) Efficacy

Data on Gene Therapy for LPLD Presented at ASGCT Annual Meeting

AMSTERDAM, May 20, 2011 - Amsterdam Molecular Therapeutics (Euronext: AMT), a leader in
the field of human gene therapy, announced today results from a long-term
efficacy study of Glybera (alipogene tiparvovec) that showed improved
chylomicron metabolism could be used as a biomarker for increased lipoprotein
lipase (LPL) activity in those patients missing the gene that produces this
protein. Glybera is a gene therapy product under development for the
treatment of lipoprotein lipase deficiency (LPLD) that is currently under
review for marketing approval with the European Medicines Agency (EMA).

In patients with mutations in the LPL gene, dietary fat
(triglyceride molecules) cannot be broken down and so cause chylomicrons,
which carry triglycerides around the body, to accumulate in the blood. This
may result in recurrent extremely painful and life-threatening episodes of
pancreatitis. Data presented last night at the American Society of Gene and
Cell Therapy 14th Annual Meeting in Seattle, USA, showed that breakdown of
chylomicrons produced after meals was greatly and significantly improved at
both 14 and 52 weeks following one-time Glybera administration.

"Lipoprotein lipase plays a central role in chylomicron
metabolism so it follows that evidence of improved long-term clearance
following Glybera administration could be taken as a measure of efficacy. It
also helps to explain the decrease in pancreatitis episodes, the most
debilitating portrayal of LPLD, seen in our clinical trials," explained Dr
Harald Petry, Head of Research at AMT.

"These data are important as they support the biological
activity of Glybera and provide a plausible mechanism of action as well as a
measurable marker of effect. We have submitted this data on chylomicron
handling to the EMA as part of our Marketing Authorisation Application. We
believe a decision by the EMA will be made by mid-2011 as previously guided,"
noted Jörn Aldag, CEO of AMT.

Study Details

A total of 5 LPLD patients were administered Glybera (1×1012
genome copies/kg, IM). At weeks 14 and 52 post-administration, patients were
given a test meal with a tracer molecule designed to monitor the breakdown of
newly formed chylomicrons in the blood. Prior to therapy, all patients
exhibited poor post-meal chylomicron handling as measured by amount seen in
the plasma over 9 hours following meal ingestion. After treatment with
Glybera, the amount of tracer found was greatly reduced and in each case was
completely eliminated within 9 hours. The effect was consistent in all
patients and sustained as observed at both the 14 and 52 week time points.

About Glybera(R)

AMT has developed Glybera as a therapy for patients with the
genetic disorder lipoprotein lipase deficiency. LPLD is an orphan disease for
which no drug treatment exists today. The disease is caused by mutations in
the LPL gene, resulting in highly decreased or absent activity of LPL protein
in patients. This protein is needed in order to break down large fat-carrying
particles that circulate in the blood after each meal. When such particles,
called chylomicrons, accumulate in the blood, they may obstruct small blood
vessels. Excess chylomicrons result in recurrent and severe acute
inflammation of the pancreas, called pancreatitis, the most debilitating
complication of LPLD. Glybera(R) has orphan drug status in EU and USA.

About Amsterdam Molecular Therapeutics

AMT is a world leader in the development of human gene based
therapies. The company's lead product Glybera(R), a gene therapy for the
treatment of lipoprotein lipase deficiency (LPLD), is currently under review
by the European Medicines Agency (EMA). If approved, Glybera will be the
first gene therapy product to be marketed in Europe. AMT also has a product
pipeline of several gene therapy products in development for hemophilia B,
Duchenne muscular dystrophy, acute intermittent porphyria, Parkinson's
disease, and SanfillipoB. Using adeno-associated viral (AAV) derived vectors
as the delivery vehicle of choice for therapeutic genes, the company has been
able to design and validate probably the world's first stable and scalable
AAV manufacturing platform. This proprietary platform can be applied to a
large number of rare (orphan) diseases caused by one faulty gene and allows
AMT to pursue its strategy of focusing on this sector of the industry. AMT
was founded in 1998 and is based in Amsterdam. Further information can be
found at www.amtbiopharma.com.

Certain statements in this press release are "forward-looking
statements" including those that refer to management's plans and expectations
for future operations, prospects and financial condition. Words such as
"strategy," "expects," "plans," "anticipates," "believes," "will,"
"continues," "estimates," "intends," "projects," "goals," "targets" and other
words of similar meaning are intended to identify such forward-looking
statements. Such statements are based on the current expectations of the
management of AMT only. Undue reliance should not be placed on these
statements because, by their nature, they are subject to known and unknown
risks and can be affected by factors that are beyond the control of AMT.
Actual results could differ materially from current expectations due to a
number of factors and uncertainties affecting AMT's business. AMT expressly
disclaims any intent or obligation to update any forward-looking statements
herein except as required by law.

PRN NLD

For further enquiries: Jorn Aldag, CEO Partner, AMT, Tel : +31-20-566-7394, j.aldag at amtbiopharma.com; Mike Sinclair, Halsin Partners, Tel : +44-20-7318-2955, msinclair at halsin.com