FDA Advisory Committee Meeting

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FDA Advisory Committee MeetingSafety
Considerations in the Development of Ultrasound
Contrast AgentsJune 24, 2008

• Nonclinical Development Program SonoVue
• Patricia D. Williams, PhD
• Chief Operating Officer
• Summit Drug Development, LLC
• Rockville, MD

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Nonclinical Development Program SonoVue

• Pharmacology studies
• Toxicology studies
• Studies on concurrent SonoVue administration and
  ultrasound exposure at high acoustic pressure
• Retrospectively (after anaphylactoid reactions
  were observed in humans) potential mechanisms of
  these reactions were studied in vitro and in vivo

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Pharmacology Studies SonoVue

• Imaging Studies to define the expected human dose
  of SonoVue (pig, dog)
• Safety pharmacology studies at multiples of human
  imaging doses (MHDbsa) 3 (mouse), 5 (rat),
  10 (rabbit), 18 (dog), 200 (monkey)
• - Cardiovascular (dog, monkey)
• - Respiratory (rat, rabbit)
• - CNS (mouse)
• - Gastrointestinal (rat)
• - Renal (rat)

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Key Findings Safety Pharmacology Studies SonoVue

• CONSCIOUS DOGS
• - No cardiovascular effects at 0.3 mL/kg
  (10-times clinical dose)
• - At 1.0 mL/kg transient hypotension in 2/7
  dogs
• ANESTHETIZED DOGS (Pulmonary Hypertension model)
• - Transient and minimal (2.5 1.3 mmHg)
  increase in
• PAP at 1 mL/kg
• No other significant Cardiovascular, CNS,
  Respiratory, GI or Renal findings in mouse, rats,
  rabbits, monkeys

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Toxicology Studies SonoVue

• Intravenous bolus administration
• Clinical formulation used
• Max doses 27-54 times the human dose (MHDbsa)
• Single dose studies (rat, monkey)
• 4-week repeated dose studies (rat, monkey)
• Genetic toxicology
• Reproductive toxicology (rat, rabbit)
• Other studies (local tolerance blood
  compatibility)

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Key Findings Toxicology Studies SonoVue

• No significant findings in single and repeat dose
  studies up to the dose of 5 mL/kg (rat, monkey)
• Repeat dose NOEL in monkeys 5 mL/kg (50 MHDbsa)
• Cecum lesions in rats considered rodent specific
  and observed with other contrast agents
  otherwise NOEL 5 mL/kg
• No signs of immunological reactions in either
  species (thymus, spleen, lymph nodes)
• No lung lesions or emboli in either species
• No brain lesions after direct injection in
  carotid artery in rats (1 mL/kg)

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Studies With SonoVue and Concurrent Ultrasound
Exposure

• RATS No histological lesions in organs with
  SonoVue (1 and 5 mL/kg) and exposed to ultrasound
  at high acoustic pressure (up to MI 1.9)
• DOGS No effect of ultrasound exposure (up to MI
  1.2) on ECG (QTc) and on heart histopathology in
  conscious dogs administered with SonoVue (up to 1
  mL/kg)

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Conclusion of the Nonclinical Animal Studies on
SonoVue

• SonoVue was well tolerated in standard
  toxicological and safety pharmacology studies
  when administered alone or with concurrent
  ultrasound exposure
• Cardiovascular effects (transient hypotension)
  observed only at very high doses in dogs (1
  mL/kg)
• Nonclinical study results corroborated the
  overall safety profile of SonoVue in humans

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Mechanism of Anaphylactoid Reactions

• Low incidence ( 0.01) of allergic-like
  (anaphylactoid) reactions in humans found in
  post-marketing surveillance
• ? Additional in vitro and animals studies were
  designed to investigate potential mechanism(s) of
  these reactions

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Mechanism of Anaphylactoid Reactions

• Hypothesis allergic-like (anaphylactoid)
  reactions are related to the particulate nature
  of ultrasound contrast agents
• Cardiopulmonary studies at imaging dose in pigs
• Cardiovascular studies at very high doses in rats
• In vitro complement activation (pig, human)
• In vitro basophil activation (human)

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The Use of the Pig Pros Cons

• Common large animal used in echocardiography (eg.
  size of heart human)
• Known to have severe reactions to injection of
  particulates
• Have high concentrations of pulmonary
  intravascular macrophages (PIMs) relative to
  other species including humans
• Imaging studies of UCA in pigs are routinely done
  with pretreatment with indomethacin or aspirin
• While useful for imaging, pig not considered as
  an animal model for safety pharmacology studies
  due to its over-reaction to all injected
  particles, however
• Based on rare human reactions, Bracco pursued
  studies in naïve pigs to possibly gain insight
  into the mechanism of these anaphylactoid
  reactions

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Changes in PAP and SAP in Pigs Following SonoVue,
and other UCAs at Imaging Doses
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Marked Individual Variations of the CV Response
to SonoVue in Pigs
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Thromboxane Release Parallels PAP Increasewith
SonoVue and another UCA
Kinetics of pulmonary arterial pressure and TXB2
changes following SonoVue or another UCA
(Product B) injections in the pig at the human
imaging dose (mean of 5 injections)
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Key Findings Mechanistic Studies Pig Model

• SonoVue and other marketed UCAs were tested on
  naïve, anesthetized pigs
• Doses in the range of 1- 4x human imaging dose
• ? SAP ? PAP ? HR
• ? Airway resistance ? Lung compliance
• Effects are dose and injection rate dependent
• ? Plasma Thromboxane B2
• No detectable increases in C3a/C5a in vivo
• Effects blocked by aspirin pretreatment
• Effects similar to other injected particulates
  (liposomes, micellar lipids, etc)

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Key Findings Mechanistic Studies Pig Model

• Marked individual variation but consistent
  response in pigs at imaging dose of UCA
• Pig shows sensitivity to SonoVue not seen in
  humans
• Symptoms cardiovascular effects resemble
  anaphylactoid reactions in humans
• Release of vasoactive mediators considered key
  event in pigs
• Relevance to humans unknown

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Key Findings Mechanistic Studies Rat Model

• Transient hypotension observed ? 5 mL/kg (25
  MHDbsa)
• ? Plasma thromboxane B2 (similar to pigs),
  however
• Hypotension NOT blocked by aspirin pretreatment
  (contrary to pigs)
• Hypotension blocked by PAF-antagonist (ABT-491)
  pretreatment (contrary to pigs)
• Hypotension blocked by complement depletion with
  cobra venom factor (CVF)
• Rats pig mechanisms may differ in mediators or
  target cells involved

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Hypotension in Rats only at High Dose Levels
Systemic arterial blood pressure changes induced
by a single administration of SonoVue in
non-anesthetized rats (Dose levels correspond to
100 300 MHDbw or 17 50 MHDbsa)
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Key Findings Mechanistic Studies In Vitro
Complement and Basophil Activation

• SonoVue and another UCA tested at very high dose
  levels show similar findings after incubation in
  vitro
• Dose-dependent increase in C3a/C5a in pig plasma
• Dose-dependent increase in C3a/C5a/SC5b-9 in
  human serum
• No marked differences between pigs humans in
  vitro
• No effects on human basophil activation (CD203c)

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Summary of Mechanistic Studies SonoVue

• Symptoms observed in pigs are similar to human
  anaphylactoid reactions (cardiopulmonary changes)
• Incidence of anaphylactoid reactions in pigs gtgtgt
  humans
• Sensitivity of pigs may be due to high density of
  PIMs relative to other species
• Rats show hypotension at very high dose
• Complement activation could be one of the
  mechanisms involved in the reactivity in rats,
  pigs and humans

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SonoVue Lessons Learned for Future

• SonoVue was well tolerated in nonclinical studies
  and this was corroborated by the clinical trials
• The lack of cardiovascular effects of SonoVue in
  safety pharmacology studies at doses relevant to
  humans correlates with the lack of anaphylactoid
  reactions in clinical trials
• Anaphylactoid reactions similar to humans are
  seen in naive pigs with various classes of
  particulate agents including UCA
• Reactions in pigs attributed to high density of
  PIMs
• The relevance of the findings in pigs to humans
  is unknown

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SonoVue Lessons Learned for Future

• In vitro complement activation may be an early
  triggering event in the reactions observed in
  humans and represents a potential screening tool
• Bracco is incorporating in vitro and in vivo
  testing in selection of next generation products
• Results in in vitro and in vivo models may be
  useful qualitatively but not quantitatively for
  risk assessment
• The rare anaphylactoid reactions may be reduced
  through these screening efforts

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• END