PharmPK Discussion - PK requirements for topical drugs

• On 13 Oct 2011 at 11:49:10, Dennis Fisher (fisher.-at-.plessthan.com) sent the message
  

  
  Colleagues
  
  One of my clients is developing a topical drug for treatment of a
  chronic cutaneous infection.  Systemic exposure to the drug is quite
  low.  In one study, a large fraction of the samples are BQL; the
  detectable concentrations are far below the concentrations associated
  with systemic administration of the drug.
  
  The company is planning a pop PK study in phase 3.  In light of the
  minimal systemic exposure, I am wondering whether this study is needed.
  Does anyone have any experience or insights into this issue?
  
  Dennis
  
  Dennis Fisher MD
  P < (The "P Less Than" Company)
  
  

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• On 13 Oct 2011 at 15:58:27, Ekaterina Gibiansky (EGibiansky.aaa.quantpharm.com) sent the message
  

  
  The following message was posted to: PharmPK
  
  Hi Dennis,
  
  I have a somewhat related experience. We had a metabolite that was a big
  safety concern, but was barely detectable. We summarized PK levels from
  the early studies (preclinical and early clinical), did some theoretical
  calculations of the highest possible levels (based on very scarce
  literature values), and showed that the levels with the desired doses of
  drug would be far below safety concerns. We went to the FDA with this
  info, and got the permission to not measure this metabolite at all in
  later clinical studies.
  
  Regads,
  Katya
  
  Ekaterina Gibiansky, Ph.D.
  CEO&CSO, QuantPharm LLC
  Web:     www.quantpharm.com
  Email:   EGibiansky at quantpharm.com
  
  

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• On 14 Oct 2011 at 05:00:24, "Dr. Prasad Tata" (drprasadtata.at.yahoo.com) sent the message
  

  
  Dear Dennis and Katya:
  
  Few years ago in AAPS annual meeting I moderated a round table discussion on PK and
  Bioanalytical requirements of drugs with Near zero bioavailability or systemic exposure.
  Speakers in this session concluded that end point or biomarker measurements and PK based
  on these end points or biomarkers is more relevant and systemic concentrations of actual
  drug or metabolites becomes supportive information.  Therefore I am thinking it is better
  to do PD measure based study would be appropriate in your situation.  Additionally Topical
  drugs need sensitization and irritation measurement studies.  I recommend that your client
  collect this information across all the studies and perform both study specific and across
  all studies summary analysis of sensitization and irritation measures.
  
  Hope this information is helpful,
  
  Prasad NV Tata, Ph.D., FCP
  AchievWin, Inc,
  2133 Seven Pines Drive
  St. Louis, MO 63134
  

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Copyright 1995-2011 David W. A. Bourne (david@boomer.org)