A phase 1, open-label, non-randomized, 2-period, fixed sequence study to investigate the absorption, metabolism and excretion of [14C-PF-04965842] and to assess the absolute bioavailability and fraction absorbed of PF-04965842 in healthy male subjects using a 14C-microtracer approach.

PF 04965842 is a new investigational compound that may eventually be used for
the treatment of eczema (atopic dermatitis) and systemic lupus erythematosus
(SLE), which is an autoimmune disease. PF 04965842 is a so-called Janus kinase
1 (JAK1) inhibitor. This means that PF 04965842 is able to inhibit the activity
of certain enzymes inside cells, including white blood cells. This will
ultimately lead to the inhibition of the production of inflammatory proteins by
these white blood cells. As a result there may be a decrease in inflammatory
processes that are characteristic for eczema and SLE. PF 04965842 is in
development and is not registered as a drug but has been given to humans
before.

The purpose of the study is to investigate how quickly and to what extent PF
04965842 is absorbed, distributed, metabolized (broken down) and eliminated
from the body (this is called pharmacokinetics). A small part of the PF
04965842 to be administered will be labeled with 14 Carbon (14C) and is thus
radioactive (also called radiolabeled). In this way PF 04965842 can be traced
in blood, urine and feces. The amount of radioactivity is negligible as
explained in Section *How much radiation will I be exposed to in this study?*.
It will also be investigated to what extent PF 049658421234 is tolerated. In
addition, the taste of PF 04965842 will be investigated.

This study will be performed in approximately 6 healthy male volunteers.

The actual study will consist of 2 periods. During the first period the
volunteers will stay in the clinical research center in Groningen (location
UMCG Hospital) for a minimum of 8 days (7 nights) and a maximum of 15 days (14
nights). During the second period they will stay in the clinical research
center in Groningen (also at the location UMCG) for 8 days (7 nights). They
will be contacted by phone for a follow-up at approximately 28 days after they
have received the study compound for the last time. The time interval between
the days on which they will receive the study compound is 10 to 17 days,
depending on the day they will leave the clinical research center.

In each period, Day 1 is the day of administration of study compound. In both
periods, the volunteers are expected at the clinical research center at 14:00 h
in the afternoon prior to the day of administration of the study compound.They
will be required not to have consumed any food or drinks during the 4 hours
prior to arrival in the clinical research center (with the exception of water).

They will leave the clinical research center between Day 7 and Day 14 in the
first period and on Day 7 in the second period. If in the first period, from
Day 6 onwards, the radioactivity levels in urine and feces are below the
pre-defined levels, they will be allowed to leave the clinical research center
earlier (thus before Day 14 in the first period).

They will be contacted by phone on Day 28 of the second period for a follow-up.

The participation to the entire study, from the pre-study screening until the
follow-up phone call will be a maximum of 12 weeks.

Not applicable.

Pain, minor bleeding, bruises and possibly an infection.