Phase IV, one-day, single blood sampling study to investigate severe thrombocytopenia and autoimmune diseases in psoriasis subjects previously treated with Raptiva (efalizumab) in the framework of the European Observational Safety Study 25878 (CLEAREST).

The EMEA requested the Company to monitor anti-efalizumab antibodies in the
context of the European Observational Cohort Study 25878 (CLEARESTTM) and also
to explore the binding of efalizumab to platelets and its effect on platelets.

Therefore, it has been agreed with the EMEA to perform the present
interventional study as and *ancillary* study to Study 25878 (CLEARESTTM).

No Investigational Medicinal Product (IMP) will be administered in the
framework of this study. The intention of this study is to gain further
information about certain safety outcomes related to previous administration of
Raptiva® as per routine European clinical practice preceding recruitment into
this trial.

Primary
To assess the prevalence of anti-efalizumab positivity in two sub-populations
of psoriatic subjects trated with Raptiva® in the framework of the CLEARESTTM
study:
- Subjects developing adverse events (AEs) corresponding to pre-specified newly
diagnosed autoimmune disorders, including (but not limited to) systemic lupus
erythematosus, Wegener*s granulomatosis, antiphospholipid syndrome, Sjögren
syndrome, rheumatoid arthritis, multiple sclerosis, Type I diabetes, autoimmune
uveoretinitis, autoimmune gust disorders such as Crohn desease or ulcerative
colitis, autoimmune vasculitis, autoimmune hepatitis, autoimmune thyroiditis
and other endocrine disorders, autoimmune haemolytic anaemia, pernicious
anaemia, myasthenia gravis, Goodpasture*s syndrome, and Guillain-Barré syndrome.
- Subjects developing severe thrombocytopenia (grade III or IV according to
National Cancer Institute * Common Toxicity Criteria for Adverse Events * i.e.,
platelet count < 50.000/mm3).

Secondary
To investigate thrombocytopenia mechanism of action in subjects who develop
severe thrombocytopenia (defined as platelet count < 50.000/mm3) in the context
of previous Raptiva® treatment in the framework of the CLEARESTTM study. For
this secondary objective, a control group of psoriasis subjects without severe
thrombocytopenia will be included.

To identify genetic profiles associated with drug-induced thrombocytopenia and
autoimmune diseases.

This study is related to the European Observational Safety Study 25878
(CLEARESTTM). Subjects from Study 25878 who developed a newly diagnosed
autoimmune disease or severe thrombocytopenia during treatment with Raptiva®
will be considered for enrolment in this study.

In addition, a control group of psoriasis subjects participating to Study 25878
without thrombocytopenia (6 subjects being currently trated with Raptiva® and 6
subjects not being currently treated with Raptiva®) will be enrolled in a few
selected centers.

Once the subjects (including the control group) have been identified and have
provided written informed consent, they will be immediately enrolled in the
study. The participation to the study will last one day which is the duration
necessary to collect the appropriate blood samples to test for anti-efalizumab
antibodies and pharmacogenetics assessments, and for subjects with severe
thrombocytopenia or belonging to the control group, to evaluate the mechanism
of action of thrombocytopenia.

- Sample collection for assessment of anti-efalizumab antibodies: for all
subjects except the control subjects.
- Sample collection for assessment of platelet counts, efalizumab-platelet
LFA-1 binding and other efalizumab- related platelet toxicity mechanisms: only
for subjects with severe thrombocytopenia and subjects from the control group.
- Sample collection for detection of genetic polymorphism (for subjects, except
the ones from the control group, consenting to the pharmacogenetic
investigation). Genetic samples and data processed will be assigned a specific
pharmacogenetic identification number (double coding), which will be accessed
by a limited number of authorized persons. This procedure will increase the
confidentiality of genetic samples and data.

The risks for these subjects are limited to mild pain and haematoma formation
at venipuncture sites which may occur within a few hours following the
collection of peripheral venous blood. This adverse reaction responds to simple
measures such as pressure and packing.

All adverse events related to the blood sampling and occurring within the first
week after the procedure are collected in the context of this trial.