Mitapivat is an oral activator of pyruvate kinase that has shown promise in treating pyruvate kinase deficiency and other hemolytic anemias. Clinical trials have found it to be well-tolerated and able to significantly increase hemoglobin levels in patients with pyruvate kinase deficiency or thalassemia. Ongoing phase 2 and 3 trials are investigating its efficacy and safety for reducing transfusions in thalassemia and decreasing symptoms in sickle cell disease.

1. PYRUVATE KINASE ACTIVATION IN
HEMOGLOBINOPATHIES
Dr/ Marwa Mahmoud Khalifa MDPHD
DMNI

2.  Most human cells generate considerable ATP from
the citric acid cycle and oxidative phosphorylation
(Aerobic glycolytic pathway)
 As erythrocytes lack mitochondria the metabolic
machinery required for aerobic metabolism, so
RBCs are largely reliant on anaerobic glycolysis for
ATP production.

3.  ATP is critical for erythrocyte cellular maintenance
and survival, its deficiency leads to premature and
pathophysiologic red cell destruction in the form of
hemolytic anemia and ineffective erythropoiesis.
 As the final enzymatic step of the Embden–
Meyerhof glycolytic pathway, the pyruvate kinase
enzyme catalyzes the conversion of
phosphenolpyruvate to pyruvate, resulting in the
generation of ATP.

5.  There are four pyruvate kinase isoforms in
mammals (red cell, liver, muscle-1, and muscle-2)
encoded by two genes (PKLR and PKM).
 Pyruvate kinase deficiency (PKD)represents the
most common glycolytic enzyme defect and the
most common congenital nonspherocytic hemolytic
anemia

6.  Other erythrocyte disorders, such as sickle cell
disease and the thalassemias, may result in a state
of increased stress and energy utilization but limited
erythrocyte ATP production adequate in normal
physiologic circumstances is no longer adequate,
causing premature cell death.
 Therefore, therapeutics capable of augmenting
erythrocyte ATP production may be useful in a
broad range of hemolytic anemias with diverse
pathophysiologies

7.  Mitapivat (AG-348) is a first-in-class, oral small
molecule allosteric activator of the pyruvate kinase
enzyme.
 Erythrocyte pyruvate kinase (PKR) is a tetramer,
physiologically activated in allosteric fashion by
fructose bisphosphate (FBP).
 Mitapivat binds to a different allosteric site from
FBP on the PKR tetramer, allowing for the
activation of both wild-type and mutant forms of the
enzyme.

8. CLINICAL TRIALS OF MITAPIVAT IN PKD

9.  multicenter, international, randomized, open-label, two-
arm dose ranging trial of AG-348 in adults with PK
deficiency
 Eligible patients are randomized to either low dose (50
mg BID) or high dose (300 mg BID) arms and receive
treatment for 6 months, with the option of extended
treatment.

10.  The trial population consists of 52 adult patients
with PK deficiency with Hb levels of ≤12.0 g/dL
(men) or ≤11.0 g/dL (women), who have received
three or fewer units of RBCs in the 12 months
preceding the first dose of mitapivat, and no
transfusion within 4 months

11.  The primary study objective was assessment of
safety and the side-effect profile. Patients were
closely followed for potential toxicities for mitapivat
with laboratory testing, electrocardiography, and
physical examination, and had DEXA scanning
 Monitoring with DEXA was done to monitor for
potential deleterious impacts of the off-target
aromatase inhibition of the drug on BMD, as well as
potential positive on-target effects on BMD from a
reduction in ineffective erythropoiesis and erythron
expansion

12. RESULTS
 Mitapivat was well-tolerated, with mild headache,
insomnia, and nausea being the most common
adverse events and resolved within a week.
 50% had a Hb increase from baseline of ⩾1.0 g/dl,
with a mean maximum increase of 3.4 g/dl, median
time was just 10 days, and improvements were
durable. Markers of hemolysis including reticulocyte
count, indirect bilirubin, and haptoglobin all
improved.
 BMD was largely stable over time in adults with
PKD receiving mitapivat up to 56 months

13. ACTIVATE trial: Global, phase 3, randomized,
placebo-controlled trial, evaluated the efficacy
and safety of mitapivat in adults with PKD who
were not receiving regular red-cell transfusions.
The patients were assigned to receive either
mitapivat (5 mg twice daily, with potential
escalation to 20 or 50 mg twice daily) or
placebo for 24 weeks.

14.  Sixteen of the 40 patients (40%) in the mitapivat
group had a hemoglobin response (an increase
from baseline of ≥1.5 g/dL sustained at two or more
scheduled assessments at weeks 16, 20, and 24)
compared with none of the 40 patients in the
placebo group

15.  ACTIVATE-T was an open-label, single-arm, phase 3 trial
conducted in 20 centres across Europe, North America,
and Asia (27 participants).
 Eligible participants were adults with PKD receiving
regular transfusions (at least six episodes in the previous
year).
 Participants received oral mitapivat during a 16-week
dose-optimization period (5 mg, 20 mg, 50 mg twice
daily) and 24-week fixed-dose period.
 The primary endpoint was a reduction in transfusion
burden (33% reduction in transfusion requirements)

16. RESULTS
 A reduction in transfusion burden by at least 33%
was found in ten (37%) participants
 The most common TEAEs were increase in ALT,
AST, headache, fatigue, and nausea.

17. CLINICAL TRIALS OF MITAPIVAT IN THALASSEMIA
AND SICKLE CELL DISEASE

18.  A phase II, open-label, multicenter study of
mitapivat in alpha- and beta-thalassemia has been
completed. This study enrolled 20 adults with non-
transfusion-dependent thalassemia with a baseline
hemoglobin of ⩽10 g/dl
 Enrolled patients began with a 24-week core
period, treated with mitapivat 50 mg twice daily with
potential dose escalation to 100 mg twice daily after
6 weeks, and could enter an open-label extension
after the 24-week core period.

19.  The primary endpoint of the study was a hemoglobin
response, defined as an increase in hemoglobin from
baseline of ⩾1.0 g/dl at any time between weeks 4 and
12 of the study. A total of 15 patients with beta-
thalassemia (2 with HbE/beta-thalassemia) and 5
patients with alpha-thalassemia were enrolled.
 The study met its primary endpoint, with 16 patients
(80%) achieving a hemoglobin response, including 11 of
the patients with beta-thalassemia and all 5 of the
patients with alpha-thalassemia. This response was
sustained in eight of the beta-thalassemia patients and
all five alpha-thalassemia patients with ongoing
treatment.

20.  Another two international, phase III, randomized,
placebo-controlled studies of mitapivat in
thalassemia are ongoing: the ENERGIZE study,
evaluating mitapivat in nontransfusion- dependent
patients with thalassemia, and the ENERGIZE-T
study, evaluating mitapivat in transfusion-
dependent patients with thalassemia.

21. PHASE I AND II ESTIMATE STUDIES OF
MITAPIVAT IN SICKLE CELL DISEASE
 A phase I multiple ascending dose study of
mitapivat in sickle cell disease, which completed in
August 2021, enrolled a total of 16 patients adults
with sickle cell disease and a baseline Hb ⩾7.0 g/dl
without transfusions or erythropoietin therapy in the
preceding 3 months were eligible.
 Stable doses of hydroxyurea and/or l-glutamine
were permitted. Enrolled patients received either
three or four ascending doses of mitapivat (5, 20,
50, and 100 mg twice daily) for 2 weeks each.

22.  The mean change in hemoglobin at the 50 mg twice
daily dose was +1.2 g/dl (range = –0.3 to +2.9 g/dl),
which returned to baseline after the drug was
tapered
 Nine of 16 patients achieved a hemoglobin
response (improvement by ⩾1.0 g/dl relative to
baseline at any dose level). Hemolytic markers
including LDH, total bilirubin, reticulocytes, and AST
similarly improved with mitapivat and normalized
after its discontinuation.

23. PHASE II ESTIMATE
 This open-label study is enrolling patients with sickle cell disease aged
16 years or older.
 A significant reduction in PoS was found (p = 0.0032). Concomitantly,
an increase in Hb-oxygen affinity was shown, reflected by a left shift of
the oxygen equilibrium curves (p = 0.0026).
 This was accompanied by a decrease in 2,3-DPG level ( p = 0.0003).
 Hb level also increased upon mitapivat treatment (mean increase
1.3 ± 0.5 g/dL; p = 0.0003). Six patients (6/8, 75%) had an increase of
≥1 g/dL from baseline, the highest was 1.9 g/dL, with five patients (5/8,
63%) reaching this increase at day 28 on mitapivat 50 mg twice daily.
 In all patients, a significant reduction in laboratory markers of
hemolysis was found,

24. RISE UP STUDY, A PHASE II/III TRIAL
A Study Evaluating the Efficacy and Safety of
Mitapivat (AG-348) in Participants With Sickle Cell
Disease is ongoing

25.  Mitapivat is a promising, first-in-class allosteric
activator of pyruvate kinase with documented safety
and efficacy across a wide spectrum of hereditary
hemolytic anemias, including PKD, alpha- and beta-
thalassemia, and sickle cell disease.