Exhibit 10.6

CONFIDENTIAL

Amendment #2 to the
Letter of Agreement between
SmithKline Beecham Corporation and
Quest Diagnostics Incorporated

1.     

The purpose of this Amendment #2 to the Letter of Agreement effective January 1,
2008 between SmithKline Beecham Corporation d/b/a GlaxoSmithKline and Quest
Diagnostics Incorporated (hereinafter the “LOA”) is to extend the term
referenced in section 2 of the LOA to the earlier of (i) June 30, 2008, or (ii)
the full execution of a new comprehensive Global Clinical Trials Agreement.

  2.     

All other terms and conditions of the LOA shall remain in full force and effect.

  3.     

The parties hereto agree to this Amendment #2 to the LOA by their authorized
signatures below.

 

SMITHKLINE BEECHAM CORPORATION   QUEST DIAGNOSTICS INCORPORATED       /s/ Paula
M. Russella   /s/ Daniel P. Megronigle   Paula M. Russella   Daniel P.
Megronigle   Sourcing Group Manager   Executive Director, Sales & Marketing    
May 21, 2008   May 15, 2008   Date   Date  

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