Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5371_Библиотеки_им_академика_М_И_Перельмана
.pdf
78
https://t.me/med1917
Chemistry and Pharmacology of Drug Discovery
1. Background
Long-acting HIV-1 antiretroviral therapy, characterized by a greater than 1-month dosing
interval, offers significant advantages over daily oral therapy. Before the emergence of
lenacapavir (1), the only long-acting HIV-1 antiretroviral therapy on the market was
Cabenuva, an extended release injectable suspension of a combination of cabotegravir
(2), an HIV integrase inhibitor, and rilpivirine (3), a non-nucleoside reverse transcriptase
inhibitor (NNRTI), given once every other month (see Chapter 3).
Nowadays, the criteria for HIV drugs to enter clinical development are very
high. Exceptional potency and low plasma clearance are required to meet dose size
requirements; excellent chemical stability and/or crystalline form stability is required to
meet formulation requirements, and new antivirals in HIV-1 therapy need to be largely
free of side effects and drug–drug interactions (DDIs).
Gilead’s HIV capsid protein inhibitor lenacapavir (1) is active at least two points
in the viral lifecycle. Thanks to its high potency and favorable pharmacokinetics (slow
sustained release and low hepatic clearance), it can be taken orally once weekly or
injected subcutaneously every 6 months while maintaining supra-effective
concentrations.
promise of being part of a complete long-acting regimen. Gilead and Merck are
collaborating to develop a long-acting HIV treatment that combines lenacapavir (1) with
Merck’s islatravir (4), a nucleoside reverse transcriptase translocation inhibitor (NRTI).
Both have long half-lives and robust virus-suppressing activity at low doses. Regrettably,
with the development of islatravir (4) slowed recently (2023) by unexpected
immunological findings, the future of this partner is far from clear.
1
However, lenacapavir (1) needs a long-acting partner if it is to deliver on the
2
79
https://t.me/med1917
Chapter 4. Lenacapavir (Sunlenca)
2. Pharmacology
The capsid core of HIV-1 is a large macromolecular assembly that surrounds the viral
genome and is an essential component of the infectious virus.
Lenacapavir (1) potently inhibited early steps of HIV-1 replication with halfmaximal effective concentration (EC
= 240 pM), antiviral activity during virus egress. Molecular modeling studies
(EC
50
predicted that lenacapavir (1) binds to the hydrophobic pocket formed by two adjoining
capsid subunits within the hexamer.
Now, let us begin learning lenacapavir (1)’s pharmacology by first scrutinizing
the structure of HIV capsid protein.
= 87 pM). It also exhibited a second, less potent
50
3
2.1. Structure of Capsid Protein
Figure 1. HIV capsid protein. Source: Zhang et al.4/MDPI/CC BY 4.0
A mature virion envelope is surround by a “fullerene cone”-shaped capsid shell that
encapsulates two copies of the positive-strand RNA genome along with associated
cellular factors and viral proteins. The HIV capsid is erected from a single protein, known
as capsid protein. Consisting of 231 residues, the HIV capsid protein (CA, p24—because
80
https://t.me/med1917
Chemistry and Pharmacology of Drug Discovery
its molecular weight is 24 kDa) forms the shell of an electron-dense, elongated core
within the virion. Capsid proteins then form pentameric and hexameric subunits, which
proceed to assemble into the mature viral capsid.
5
After the budding of the immature virion, proteolytic processing (maturation) of
the Gag polyprotein causes the rearrangement of the capsid proteins into a conical core
structure that surrounds the viral genome in the mature virus. The mature core comprises
approximately 1500 capsid monomers with about 250 capsid hexamers and 12 capsid
4
pentamers (Figure
1).
Capsid consists of two domains called the N-terminal domain (NTD) and Cterminal domain (CTD), with a flexible linker connecting both. On the other hand, capsid
NTD consists of seven α-helices, a β-fold, and a cyclophilin A (CypA) binding loop,
while capsid CTD consists of a 310 helix, four α-helices, and an N-terminal extension
chain. CypA was found to bind Gag in the capsid region back in 1993.
6
2.2 Functions of Capsid Protein
Capsid does not have known catalytic activity although it can impact multiple viral
enzymatic activities, including that of reverse transcriptase and integrase. HIV capsid
protein serves critical roles in many aspects of the HIV-1 replication cycle such as
reverse transcription, cytoplasmic transport, nuclear entry, and virion maturation in
addition to interacting with over 20 host factors essential for infection.
6
2.2.1. At the Early Stages of the Virus Life-Cycle
The HIV-1 capsid houses the replicative enzymes and viral genomic RNA, protecting
them from antiviral factors and cellular sensors of innate immunity, allowing their traffic
from entry to near integration sites before fully uncoating. Increasing evidence suggests
that the capsid participates in the translocation of viral genomic material into the host
nucleus for integration through partial uncoating that allows higher plasticity of the
7
capsid.
by the protease enzyme. It is initially expressed within the Gag and Gag–Pol polyproteins
and provides key interactions between proteins that are necessary for assembly of the
virion. HIV-1 Gag proteins are necessary for virion assembly, virion maturation, and
early stages of virus replication.
process known as disassembly, in which capsid dissociates and releases its contents into
the cytoplasm. Specifically, following fusion of the viral particle with the target cell
membrane, the HIV-1 capsid core is released into the cytosol where it protects the viral
genome and enzymes from host defenses while trafficking these contents along the
As mentioned before, capsid is generated by the cleavage of the Gag polyprotein
When a virus enters the cytoplasm of a cell, it undergoes a highly controlled
81
https://t.me/med1917
microtubule network toward the nucleus. These replication steps require capsid to interact
with human factors such as CypA, nucleoporins 153 and 358 (NUP153, NUP358),
cleavage and polyadenylation-specific factor 6 (CPSF6), and other factors (Figure
Chapter 4. Lenacapavir (Sunlenca)
2).
Figure 2. Schematic overview of the early stages of HIV-1 replication. Source: Zhuang
2.2.2. At the Late Stages of the Virus Life-Cycle
The late phase of the HIV-1 life cycle begins with transcription of the provirus, followed
by export of the synthesized RNA to the cytoplasm and translation of the Gag/Gag–Pol
polyproteins. In the final phase of maturation, capsid is at first expressed within the
Gag/Gag–Pol polyproteins and provides key interactions between proteins that are
and Torbett
6
/MDPI/CC BY 4.0
82
https://t.me/med1917
Chemistry and Pharmacology of Drug Discovery
necessary for assembly of the virion. Gag is cleaved and capsid is released, allowing the
8
assembly of capsid into a “fullerene cone,” known as the capsid core.
In view of the key functions of the capsid protein, it has become a popular target
9
for the development novel anti-HIV drugs.
Moreover, interfering with only a few of
these capsid–capsid interactions is thus expected to reduce HIV infectiousness severely.
As a comparison, each viral particle contains approximately 250 integrase proteins, of
which only four need to be functionally active to achieve the irreversible integration of
HIV DNA in the human genome.
2.3. Capsid Protein Inhibitors
The interactions between capsid proteins are the key determinants for the stability of the
mature capsid, which is essential for the precise timing of the assembly and uncoating
steps in the HIV-1 life cycle. Thus, creating small molecules that either stabilize or
destabilize the capsid core is a promising strategy for the discovery of novel antiviral
treatments.
capsid protein region involved in self-assembly has been defined within the past decade.
This pocket within the assembled hexamer and pentamer is the binding site for host
dependency factors. Disruption of the interactions of capsid with host factors could
interfere with HIV-1 replication. Moreover, the NTD–CTD interface is also the binding
site of extensively studied small molecule modulators such as lenacapavir (1) and PF3450074 (PF74, 5).
peptidomimetic compound built around a phenylalanine core and capped with indole-3acetic acid and aniline moieties at the amino and carboxylate ends, respectively.
6
The NTD–CTD interprotomer pocket, a particularly therapeutically attractive
In 2010, Pfizer reported that PF74 (5) exhibited antiretroviral activity. It is a
Cocrystal structures revealed that (S)-PF74 (5) binds to a novel binding pocket
in the NTD of the protein. This hydrophobic cavity, also known as the phenylalanineglycine (FG) binding pocket, is the same binding site of lenacapavir (1). (S)-PF74 (5) also
binds to the cellular HIV-1 cofactors that mediate nuclear import of pre-integration
complexes (PICs). Since (S)-PF74 (5) interferes with both capsid assembly and
83
https://t.me/med1917
Chapter 4. Lenacapavir (Sunlenca)
disassembly, it inhibits both the early (virion uncoating) and late (viral core assembly)
events in the viral replication cycle.
10
The (S)-PF74 (5) inhibits viral replication via two distinct mechanisms of action:
by disrupting CA–CA interactions, they could alter the overall core stability and impact
viral assembly and uncoating; by competing against NUP153 and CPSF6 for capsid
binding, they could block viral nuclear entry and/or productive integration. In addition to
(S)-PF74 (5), many capsid protein inhibitors, especially the ones binding to the FG
11
pocket, have been reported.
Clinical trials of (S)-PF74 (5) was carried out but was terminated during phase I.
2.4. Lenacapavir
Employing (S)-PF74 (5) as the starting point and drawing on X-ray crystallographic
information, Gilead designed lenacapavir (1) to bind tightly at a conserved interface
between capsid protein monomers. Lenacapavir (1) reduces viral replication at both the
early and late stages of the HIV life cycle by binding at the interface between two capsid
proteins. This binding interferes with capsid-mediated interactions between proteins that
are essential for multiple phases of the viral replication cycle (Figure
3).
7
Figure 3. The X-ray crystal structure of the HIV-1 capsid hexamer bound to PF-3450074
(5, PDB code: 4XFZ) and lenacapavir (1, PDB code: 6V2F). Source: McFadden et
Just like (S)-PF74 (5), lenacapavir (1) inhibits HIV-1 replication mainly by
binding to the FG binding site, stabilizing and thereby preventing capsid disassembly in
infected T cells.
It is a tight inhibitor (with picomolar potency) that binds two contiguous capsid
subunits while promoting distal intra- and inter-hexamer interactions that stabilize the
curved capsid lattice. A crystal structure of lenacapavir (1) bound to a cross-linked capsid
7
/Springer Nature/CC BY 4.0
al.
84
https://t.me/med1917
Chemistry and Pharmacology of Drug Discovery
hexamer shows extensive hydrophobic and electrostatic interactions, seven hydrogen
bonds, and two cation–π interactions between lenacapavir (1) and residues of binding site
3
1 (Figure
4).
Figure 4. The X-ray crystal structure of the HIV-1 capsid hexamer bound to lenacapavir
(1, PDB code: 6V2F). Source: Link et al.
Inspired by lenacapavir (1)’s spectacular success, “me-too” drugs soon emerged.
ViiV’s capsid inhibitor ViiV-1 (6) also binds to the now-familiar hydrophobic FG
7
pocket.
In the same vein, BMS/ViiV in 2023 published their potent long-acting
inhibitors targeting the HIV-1 capsid based on a versatile quinazolin-4-one scaffold. The
development candidate GSK878 (7) has an EC
3
/with permission of Springer Nature
value of 39 pM.12
50
85
https://t.me/med1917
Chapter 4. Lenacapavir (Sunlenca)
3. Structure–Activity Relationship (SAR)
Gilead has not yet published any SAR for this series of capsid inhibitors at the time of
writing of this review (2023). In lieu of SAR, the progression of the project is
summarized here according to John Link’s seminar presentation at the 2023 Steamboat
Medicinal and Bioorganic Chemistry Conference in Steamboat, Colorado.
In the hands of Gilead scientists, (S)-PF74 (5) was tested as an accelerator, not
an inhibitor, of capsid assembly. Its EC
cytotoxicity concentration, CC
= 32 μM, providing a therapeutic window of 26.
50
in MT-4 cells was 1.24 μM whereas its
50
In order to quickly evaluate the SAR of the indole motif, a parallel synthesis was
carried out to prepare an array of derivatives at Gilead. Among them, dipeptide 8 with a
5-OH-substituted indole showed a 25× boost of potency (EC
= 52 nM). However, the
50
86
https://t.me/med1917
presence of the phenol functionality on dipeptide 8 led to extensive phase II metabolism
through formation of the corresponding 5-OH glucuronide, accompanied by amide bond
cleavage.
Scrutinizing the X-ray crystal structure of binding pose of dipeptide 8 to capsid
protein, it was realized that the amide bond could be rigidified to afford pyridine 9, which
only had one amide bond left. Another parallel synthesis led to carboxamide 10 with its
primary amide forming a hydrogen bond with histidine-75 of the capsid protein, which
became known as a potency driver.
Chemistry and Pharmacology of Drug Discovery
While carboxamide 10 was more potent than its precursor, it saw significant
(70%) metabolism-based inhibition (MBI). Not only did this metabolism pose potential
toxicity issue, but it also had DDI potential. As shown below, it is reasonable to assume
that amide 10 was initially oxidized at the “benzylic” position by CYP3A to the
corresponding alcohol 11. This unstable alcohol then underwent an elimination process to
provide enamide 12 as the proposed metabolite, which then potentially formed a covalent
bond with a nucleophile of CYP3A to inactivate the enzyme.
87
https://t.me/med1917
After extensive exploration, it was found that cyclohexyl ring-fused pyrazole 13
did not suffer MBI (<1%) as did amide 10. But it was extensively metabolized/cleared. In
order to explore the metabolic “soft spots,” the suspected cyclohexyl ring was removed to
afford the “naked” pyrazole 14, which completed lost its potency in MT-4 cells but its
metabolic stability was significantly improved—indicating that the cyclohexyl ring on
pyrazole 13 contained indeed the “soft spots.”
Chapter 4. Lenacapavir (Sunlenca)
In an attempt to block the metabolic “soft spots,” tetrafluorocyclohexyl 15 was
prepared, which eventually morphed into the tricyclic cyclopropyl 16. It enjoyed both
good potency and stability.
Gilead’s efforts to enhance potency led to modifications on the right-hand
portion of the molecules. Aminoindazole 17 was nearly 10× more potent than its
Соседние файлы в папке Библиотека им академика М.И. Перельмана