[BioTime, Inc.]{.smallcaps}

Blood Products Advisory Committee

13-14 June 2002

BioTime, Inc. Summary

Hextend^®^ (Table 1) was approved for marketing as a plasma volume
expander in the United States on March 31, 1999 (OB-NDA 20-0952). The
following evidence demonstrates that Hextend^®^ (6% Hetastarch in
Lactated Electrolyte Injection) should not receive a warning label for
bleeding and is pharmacologically different than 6% hetastarch in 0.9%
sodium chloride. The data indicate that Hextend^®^ is equivalent to 5%
albumin and superior to 6% hetastarch in 0.9% sodium chloride with
respect to blood product usage and effects on coagulation.

  ------------------------------- ----------------- ---------------------
  Table 1                         HEXTEND^®^        6% hetastarch in 0.9%
                                                    sodium chloride

  Hetastarch (g/L)                60                60

  Sodium (mEq/L)                  143               154

  Chloride (mEq/L)                124               154

  Lactate (mEq/L)                 28                

  Calcium (mEq/L)                 5                 

  Potassium (mEq/L)               3                 

  Magnesium (mEq/L)               0.9               

  Dextrose Hydrous (mg/dL)        99                
  ------------------------------- ----------------- ---------------------

With respect to bleeding in cardiac surgery, a prospective, randomized,
blinded clinical trial to study the intraoperative use of large volumes
of surgical fluids was performed at Columbia University by Dr. Elliott
Bennett-Guerrero and colleagues \[1, 2\]. This study was summarized in
Anesthesiology News Special Reports \[3, 4\]. The 200 patients
undergoing coronary bypass graft and/or valvular heart surgery were
randomized to one of four fluids for intraoperative fluid management: 5%
albumin in 0.9% sodium chloride, lactated Ringer's, 6% hetastarch in
0.9% sodium chloride (HES/NS), and 6% hetastarch in a balanced
electrolyte formulation (Hextend^®^). Each group received a similar
amount of study fluid (approximately 3-4 L) \[1\].

In the perioperative period (OR + 24 hr), the HES/NS patients received a
median 4 units of pRBC (interquartile range \[IQR\], 2-6), 3 units of
FFP (IQR, 0-6) and 6 units of platelets (IQR, 0-9), as compared to the
Hextend^®^-treated patients who received 2 units of pRBC (IQR, 0-2), 0
units of FFP (IQR, 0-4.5) and 0 units of platelets (IQR, 0-6). The
differences in pRBC and FFP received by HES/NS and Hextend^®^ patients
were significant (p\<0.05). Albumin-treated patients received a median 2
units of pRBC (IQR, 0-2), 0 units of FFP (IQR, 0-4) and 0 units of
platelets (IQR, 0-6), the same as those treated with Hextend^®^.

Although the preoperative serum creatinine values were similar for both
groups, (HES/NS = 1.0 ± 0.3 mg/dL; Hextend^®^ 1.0 ± 0.2 mg/dL), at one
week after surgery there was a significant difference in serum
creatinine values (HES/NS = 1.5 ± 0.7 mg/dL; Hextend^®^ = 0.9 ± 0.2
mg/dL; p \<0.05). Also, when compared with patients treated with 5%
albumin in 0.9% sodium chloride, the Hextend^®^ patients had better
renal function, reduced postoperative pain and nausea and more rapid
return of gastrointestinal function.

A small study by K C Petroni et al. \[5\], supports the assertion that
with regard to blood product usage Hextend^®^ is similar to 5% albumin
in Ringer's lactate. In the Petroni study 28 patients undergoing
elective cardiac surgery were randomized to receive either Hextend^®^ or
5% albumin as their intraoperative and post operative volume expander
for up to 24 hours post surgery. There was no difference in chest tube
output, pre- and post-op hematocrits or blood product usage.

In a prospective, randomized, double-blinded Phase III clinical trial
conducted for NDA approval, Hextend^®^ and 6% hetastarch in 0.9% sodium
chloride were found to be equivalent with regard to plasma volume
expansion \[6\]. 120 patients undergoing elective non-cardiac surgery
were treated either with Hextend^®^ (1.6 ± 1.0 L) or 6% hetastarch in
0.9% sodium chloride (1.4 ± 1.1 L). The study was designed to determine
the safety and efficacy of Hextend^®^ in surgeries generally accompanied
by blood losses in excess of 500 mL. However, not all patients required
blood or blood products. When the transfused subset was analyzed, the
Hextend^®^ treated patients who received 2.1 ± 1.0L of solution lost
less blood (1.6 ± 1.0 L vs 2.5 ± 1.9 L, p =0.02) and had a lower blood
product usage than those patients who received a similar volume (2.2 ±
1.2L) of 6% hetastarch in 0.9% sodium chloride.

Though there were no overall differences in laboratory hematologic and
coagulation variables, there were measurable differences in the number
of patients in the transfused group who received calcium, and in the
amount of calcium received: Hextend^®^ (1 patient, 250 mg); 6%
hetastarch in 0.9% sodium chloride (6 patients, 2200 ± 714 mg, mean ±
SEM). Also, in patients who received ≥20 mL/kg of study fluid, the onset
of clot formation (r time) measured by thromboelastography (TEG) was
significantly slower in patients who received 6% hetastarch in 0.9%
sodium chloride \[6\].

In a smaller study targeting coagulation by T J Gan et al. \[7\],
Hextend^®^ was shown to be similar to 5% albumin in 0.9% sodium
chloride. In this study patients undergoing radical retropubic
prostatectomy or radical nephrectomy were randomly assigned to receive
either Hextend^®^ or 5% albumin in 0.9% sodium chloride as the
intraoperative colloidal solution. Fourteen patients received Hextend^®^
(2.5 ± 1.4 L) and 11 patients received 5% albumin in 0.9% sodium
chloride (1.8 ± 1.0 L). There were no significant differences in PT,
aPTT, Factor VIII, von Willebrand factor activity or antigen or in
platelet function tests between the Hextend^®^ and albumin groups at the
end of surgery or at 24 hours post surgery.

Hextend^®^, 6% hetastarch in 0.9% sodium chloride and Ringer's lactate
were compared for effects on coagulation by thromboelastography (TEG)
after in vitro dilutions of human blood ranging from 20 to 75% \[8\].
The rate of initial fibrin formation (r time) was slowed when the
dilution with 6% hetastarch was ≥ 50%. At 75% dilution the 6% hetastarch
samples failed to clot, while the Hextend^®^ samples exhibited r times
similar to undiluted fresh whole blood that was used as control (8).
These data are consistent with the observation that in the Phase III
study patients receiving larger volumes of 6% hetastarch had a larger
blood loss \[6\]. The six 6% hetastarch in 0.9% sodium chloride treated
patients, who received supplementary calcium, averaged 3150 ± 626 mL of
study fluid had an estimated blood loss of 4817 ± 883 mL and received an
average of 3150 ± 730 mL of blood.

Another comparison of the coagulation effects of balanced electrolyte
formulations versus a variety of saline-based fluids on hemodilution of
human blood in vitro using TEG, indicated that blood samples diluted
with 6% hetastarch in 0.9% sodium chloride (40-60% dilution) had a
significantly slower r time (rate of initial fibrin formation) than did
those diluted with Hextend^®^ (9, 10). At 60% dilution albumin had an r
time \> 60 minutes, as did all the saline-based solutions at 80%
dilution. Addition of calcium tended to correct the r times. This is
consistent with the data from the transfused group of the Hextend^®^
Phase III study with regard to blood loss, the TEG data and the calcium
requirements (6), and may explain why volume for volume, 6% hetastarch
in 0.9% sodium chloride causes a greater need for blood and blood
products than Hextend^®^.

As the data in Table 1 indicate, Hextend^®^ is formulated differently
than 6% hetastarch in 0.9% sodium chloride. This difference in
formulation results in a different product pharmacologically. For
example, patients treated with Hextend^®^ exhibit less blood loss and
have better renal function \[1-4, 6\], as well as a lower incidence of
hyperchloremic metabolic acidosis \[11\] than patients treated with 6%
hetastarch in 0.9% sodium chloride.

In a prospective, randomized, blinded study \[11\] of 47 elderly
patients undergoing major elective non-cardiac surgery and receiving
large volumes of intraoperative colloidal solutions, patients treated
with 6% hetastarch in 0.9% sodium chloride (2.5 ± 1.2 L) and 0.9% sodium
chloride as a crystalloid were compared with those treated with
Hextend^®^ (2.4 ± 1.2 L) and Ringer's lactate. The study was designed to
identify differences in blood biochemistry and acid-base balance. In the
6% hetastarch in 0.9% sodium chloride group, the postoperative serum
chloride levels were higher (9.8 vs 3.3 mmol/L, p = 0.0001),
postoperative standard base excess decreased more (-5.5 vs -0.9 mmol/L,
p = 0.0001) and the incidence of postoperative hyperchloremic metabolic
acidosis was greater (66% vs 0%, p = 0.0001) compared to preoperative
levels.

Furthermore, a retrospective analysis of the Hextend^®^ Phase III study
\[6\] confirmed that even with a background of lactated Ringer's
solution, the Hextend^®^-treated patients had fewer incidences of
metabolic acidosis (10 vs 20, p\<0.05) and hyperchloremic metabolic
acidosis (2 vs 8) than those patients who received 6% hetastarch in 0.9%
sodium chloride

Thus, surgical patients treated with Hextend^®^ lost less blood and had
a reduced requirement for blood products, better renal function and less
hyperchloremic metabolic acidosis compared to patients treated with 6%
hetastarch in 0.9% sodium chloride, Compared to those treated with
albumin, Hextend^®^ patients had a similar requirement for blood and
blood products, lost similar quantities of blood during cardiac surgery,
but had a superior outcome regarding renal function, postoperative pain
and nausea, and return of gastrointestinal function.

With regard to the issue of bleeding, the clinical trials demonstrate
that both in cardiac surgery and non-cardiac elective surgery patients
treated with Hextend^®^ versus 6% hetastarch in 0.9% sodium chloride had
significantly less loss of blood and less need for blood and blood
products. The TEG data from both the clinical studies and the in vitro
hemodilution studies indicate that Hextend^®^ causes less of a reduction
in the rate of fibrin formation. These data are consistent with the
clinical data and may provide a mechanism for the difference in bleeding
seen clinically. The clinical data and the coagulation data indicate
that Hextend^®^ is comparable to 5% albumin with regard to its effect on
blood coagulation and blood product usage.

The conclusion from all these studies is that Hextend^®^ is a different
product than 6% hetastarch in 0.9% in sodium chloride and not simply
starch in saline, and thus should not receive a warning label that
indicates it causes bleeding.

References

1.  Bennett-Guerrero, E., et al. Impact of Normal Saline-Based Versus
    Balanced Salt Fluid Replacement on Postoperative Renal Function:
    Randomized Trial Preliminary Results. Anesth Analg 2001;92,SCA129.

2.  Bennett-Guerrero, E., et al. Impact of Normal Saline Based Versus
    Balanced-Salt Intravenous Fluid Replacement on Clinical Outcomes: A
    Randomized Blinded Clinical Trial. Anesthesiology 2001;95:A147.

3.  Special Report: Volume Replacement Issues. Anesthesiology News 2001;
    27:1-8.

4.  Special Report: Issues in Fluid Volume Replacement. Anesthesiology
    News 2002; 28:1-8.

5.  Petroni, Kenneth C., et al. Hextend^®^ Is a Safe Alternative to 5%
    Human Albumin for Patients Undergoing Elective Cardiac Surgery.
    Anesthesiology 2001; 95:A198.

6.  Gan, T.J. et al Hextend^®^, a Physiologically Balanced Plasma
    Expander for Large Volume Use in Major Surgery: A Randomized Phase
    III Clinical Trial. Anesth Analg 1999;88:992-8.

7.  Gan, T.J. et al. Randomized Comparison of the Coagulation Profile
    When Hextend^®^ or 5% Albumin is Used for Intraoperative Fluid
    Resuscitation. Anesthesiology 2001; 95:A193.

8.  Roche, Anthony M. Privileged Communication

9.  Roche, Anthony M. et al. Comparison of the Coagulation Effects of
    Balanced Electrolyte Versus Saline-Based Fluid Haemodilution Using
    TEG® *In Vitro.* Anesthesiology 2001; 95:A199.

10. Roche, Anthony M. Privileged Communication

11. Wilkes, Nicholas J., et al.The Effects of Balanced Versus
    Saline-Based Hetastarch and Crystalloid Solutions on Acid-Base and
    Electrolyte Status and Gastric Mucosal Perfusion in Elderly Surgical
    Patients. Anesth Analg 2001; 93:811-6.

12. Segall, Judith and Powanda, Michael C. Retrospective Analysis of
    U.S. Phase III Clinical Study of Hextend^®^ Assessment of Incidence
    of Metabolic Acidosis and Hyperchloremic Metabolic Acidosis. BioTime
    Report 0101.

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