Highlights on the Development, Related Patents, and Prospects of Lenacapavir: The First-in-Class HIV-1 Capsid Inhibitor for the Treatment of Multi-Drug-Resistant HIV-1 Infection

The multidrug-resistant (MDR) human immunodeficiency virus 1 (HIV-1) infection is an unmet medical need. HIV-1 capsid plays an important role at different stages of the HIV-1 replication cycle and is an attractive drug target for developing therapies against MDR HIV-1 infection. Lenacapavir (LEN) is the first-in-class HIV-1 capsid inhibitor approved by the USFDA, EMA, and Health Canada for treating MDR HIV-1 infection. This article highlights the development, pharmaceutical aspects, clinical studies, patent literature, and future directions on LEN-based therapies. The literature for this review was collected from PubMed, authentic websites (USFDA, EMA, Health Canada, Gilead, and NIH), and the free patent database (Espacenet, USPTO, and Patent scope). LEN has been developed by Gilead and is marketed as Sunlenca (tablet and subcutaneous injection). The long-acting and patient-compliant LEN demonstrated a low level of drug-related mutations, is active against MDR HIV-1 infection, and does not reveal cross-resistance to other anti-HIV drugs. LEN is also an excellent drug for patients having difficult or limited access to healthcare facilities. The literature has established additive/synergistic effects of combining LEN with rilpivirine, cabotegravir, islatravir, bictegravir, and tenofovir. HIV-1 infection may be accompanied by opportunistic infections such as tuberculosis (TB). The associated diseases make HIV treatment complex and warrant drug interaction studies (drug–drug, drug–food, and drug–disease interaction). Many inventions on different aspects of LEN have been claimed in patent literature. However, there is a great scope for developing more inventions related to the drug combination of LEN with anti-HIV/anti-TB drugs in a single dosage form, new formulations, and methods of treating HIV and TB co-infection. Additional research may provide more LEN-based treatments with favorable pharmacokinetic parameters for MDR HIV-1 infections and associated opportunistic infections such as TB.


Introduction
Human immunodeficiency virus (HIV) infection is one of the important public health concerns. HIV-1 and HIV-2 are two genetically distinct types of HIV, wherein the global prevalence of HIV-1 infection (about 95%) is more than HIV-2 [1]. Worldwide, approximately 38.4 million people are afflicted with HIV-1 infection, with approximately 28.7 million receiving antiretroviral therapy (ART) [2]. The HIV-1 infection weakens the immune system of infected people and may progress to acquired immunodeficiency syndrome (AIDS). AIDS is characterized by a CD4+ T-cell count of <200 cells per microliter or HIV infection with associated diseases (tuberculosis, cryptococcal meningitis, lymphomas, Kaposi's sarcoma, etc.). The increased viral load of HIV-1 and decreased CD4+ T-cell count are the principal markers of HIV-1 infection progression or treatment failure [3]. When left untreated, HIV-1 infection or AIDS can also lead to death after a latency period of various lengths. The HIV-1 infection can be managed but not cured by ART regimens/classes ( Figure 1) [4][5][6][7][8]. The increased use of ART has been supplemented by the development of drug resistance, including multi-drug resistance (MDR), in recent years. The unaddressed drug resistance threatens the efficacy of ART and can lead to a rise in new HIV-1 infections and HIV-related morbidity and mortality [9]. The MDR HIV-1 infection (unmet medical need) is refractory to current ART and demands the development of new treatments [10]. Recently, the United States Food and Drug Administration (USFDA). Health Canada and the European Medicines Agency (EMA) have approved Lenacapavir (LEN) as the first-inclass capsid inhibitor for the treatment of MDR HIV-1 infection [11][12][13][14]. Some reviews on LEN have been published, but they are silent about the pharmaceutical aspects, inventions, and patent literature of LEN [11][12][13][15][16][17][18][19]. This review highlights the pharmaceutical aspects, development, related patents, and prospects for LEN. The literature for this review was collected from PubMed, authentic websites (USFDA, Health

HIV-1 Transmission
Unprotected sex, sharing needles to inject drugs, infected mother to her child during pregnancy, exchange of contaminated fluid from infected people (blood, breast milk, semen, vaginal secretion) Signs and symptoms Fever, sore throat, swollen lymph nodes, rash, muscle ache, night sweat, mouth ulcers, chills, and fatigue Diagnosis Antibody test, antigen/antibody test, and nucleic acid test

Lenacapavir
Sunlenca injection (the sterile and preservative-free clear yellowish-brown s LEN has three chiral centers and can exist in eight stereoisomeric forms. The (2S,3bS,4aR)isomer is the main isomeric active ingredient of Sunlenca. Different polymorphs (crystalline, amorphous, solvates, etc.) of LEN are reported. Sunlenca contains crystalline LEN sodium as the active ingredient due to its convenient features, reproducibility, stability (oxidative, hydrolytic, and photolytic), and biopharmaceutical characteristics [20,21].
Sunlenca injection (the sterile and preservative-free clear yellowish-brown solution) contains polyethylene glycol 300 and water for injection as additional non-medicinal ingredients. Sunlenca tablet (beige, capsule-shaped film-coated tablet) also contains many additional non-medicinal ingredients [20,24,25].

Mechanism of Action of LEN
HIV-1 is an enveloped retrovirus. The HIV-1 capsid (a protein shell) contains viral RNA, nucleocapsid, reverse transcriptase, and integrase ( Figure 3) [26][27][28]. This HIV-1 capsid contributes to multiple essential processes during different stages of HIV-1 replication, including protecting, transporting, interacting with the host cell, and releasing the viral genome in the host cell ( Figure 4) [18,26,29]. A deficiency in the normal function of the HIV-1 capsid impedes different aspects of the HIV-1 life cycle, including the nuclear uptake and integration of viral DNA into the host genome. These features of HIV-1 capsid make it a potential drug target for developing anti-HIV agents [30][31][32].
OR PEER REVIEW 5 of 17  The protein capsid of HIV-1 comprises repeating subunits called protomers (hexamer). LEN selectively binds at the interface of two hexamer subunits (N74 residue of the Nterminal domain of one hexamer and two residues (N183 and K70) of the C-terminal domain of neighboring hexamer) of HIV-1 capsid [33,34]. This phenomenon causes the development of immature HIV-1 capsid or its inhibition and, ultimately, inhibition of various functions of HIV-1 capsid at different stages of the replication cycle of HIV-1 ( Figure 4). Accordingly, LEN interferes at multiple stages of the HIV-1 life cycle, including capsid-mediated nuclear uptake of HIV-1, virus assembly and release, and capsid core formation ( Figure 4).
The pharmacokinetic data of LEN in the animal models (Sprague-Dawley rats, Beagle dogs, and Cynomologous monkeys) is disclosed in the patent/patent application file by Gilead and the documents published by the USFDA, EMA, and Health Canada [20,24,25,36,37]. LEN was tested in dogs (100 mg/kg) for the assessment of its effect on the heart (blood pressure, heart rate, ECG, QT, and QTc) and rats (100 mg/kg and 10 mg/kg) for the assessment of its effect on the central nervous system and respiratory system. These animal-based studies revealed no significant concern for the heart, CNS, and respiratory systems. LEN demonstrated no effects on animal fertility and was non-carcinogenic and non-mutagenic.

Clinical Studies on LEN
We searched the clinical trial database and Gilead's website using the abovementioned keywords [14,40]. This search provided eight clinical studies on LEN (Table 3).  The data of the clinical phase 1 study (NCT03739866) is available on the clinical trial website and in the literature [35]. This study demonstrated LEN's safety, efficacy, and appreciable pharmacokinetic parameters.
The clinical phase 2 data (NCT04143594) of the combination of LEN with other ART has been published [16,41]. A virological suppression of 85-92% was observed after 54 weeks with the combination of LEN with different ARTs (emtricitabine, tenofovir, and bictegravir). The study revealed headache and nausea as the most frequent adverse events with oral treatment, whereas erythema, swelling, and pain were associated with SC administration of LEN.
The clinical phase 3 data of NCT04150068 is recently published [19]. This study was performed on MDR HIV-1 patients. The LEN-treated group displayed a greater reduction of the viral load in >81% of the patient than the placebo group. A commentary on the ongoing clinical phase 3 data of LEN (NCT04925752, Purpose 2 trial) has been publicized [42]. However, this study is silent about the conclusive and full outcomes of the study.
A proof-of-concept clinical trial has also been performed that analyzed the activity of LEN against LEN-associated resistance mutations [43]. This study revealed a beneficial inverse association between the replication capacity of HIV-1 and drug resistance. This study also revealed capsid mutation (Q67H) development with LEN monotherapy in two participants.

Food Interactions
The tablet may be taken with or without food [20,24,25].

Warning/Precautions
Immune reconstitution syndrome and autoimmune disorders such as Grave's disease, autoimmune hepatitis, and polymyositis. Non-adherence to the recommended dose can cause drug resistance [20,24,25].

Toxicity/Overdose
Limited data is available on the toxicity of LEN. Toxicity treatment is based on signs and symptoms, along with supportive care. Dialysis may not be effective because LEN is a highly protein-bound drug. No cardiotoxicity is reported using LEN [20,24,25].

Special population
No study has been carried out on the effect of LEN among the elderly, pediatric, and pregnant/breastfeeding women population [20,24,25].

The Development Cycle of LEN
The important event (patent filing, clinical trials, and drug regulatory affairs) of LEN is depicted in Figure 5.

Special population
No study has been carried out on the effect of LEN among the elderly, pediatric, and pregnant/breastfeeding women population [20,24,25].

The Development Cycle of LEN
The important event (patent filing, clinical trials, and drug regulatory affairs) of LEN is depicted in Figure 5.

Patent Literature
The patent search was conducted on 9 February 2023, using different keywords of LEN (GS-6207, GS-714207, lenacapavir, Sunlenca, and J05-AX31) on different patent databases, including USPTO, Espacenet, and Patent scope [45][46][47][48]. When the USFDA approves a drug, the innovator also provides a list of relevant patents related to the approved drug products to the USFDA. The USFDA lists these patents in the Orange Book Database (OBD) [49,50]. The OBD was also searched to get information about the relevant

Patent Literature
The patent search was conducted on 9 February 2023, using different keywords of LEN (GS-6207, GS-714207, lenacapavir, Sunlenca, and J05-AX31) on different patent databases, including USPTO, Espacenet, and Patent scope [45][46][47][48]. When the USFDA approves a drug, the innovator also provides a list of relevant patents related to the approved drug products to the USFDA. The USFDA lists these patents in the Orange Book Database (OBD) [49,50]. The OBD was also searched to get information about the relevant patents related to Sunlenca. The patents/patent applications that specifically mentioned LEN-based inventions in their claim directly or indirectly were segregated. The redundant/duplicate patents/patent applications were removed, and the remaining patent documents are summarized in Table 5.   A method of treating HIV-1 infection in a heavily treatment-experienced patient (e.g., patients with MDR HIV infection) with a therapeutically amount of LEN or its pharmaceutically acceptable salt alone or in combination with a protease inhibitor, NNRTI, NRTI, integrase inhibitor, and pharmacokinetic enhancers [36].

WO2022159877A1 (Brii Biosciences; 25 January 2022)
A combination of capsid inhibitors (LEN) and an adenosine derivative (islatravir. an NRTI) for the treatment/prevention of HIV infection. This patent application is silent about the experimental details of the combination of LEN and islatravir [58].  A method of treating HIV infection with a long-acting pharmaceutical formulation of tenofovir alafenamide containing sucrose acetate isobutyrate, which may optionally contain a capsid inhibitor (LEN). This patent application is silent about the experimental details of the combination of LEN and tenofovir [62]. WO2020247933A2 (Univ Missouri;8 June 2020) This patent application claims cyclic or linear peptides as HIV-1 capsid inhibitors [63].

Discussion
HIV/AIDS-related morbidity and mortality have decreased over the last two decades. However, the MDR HIV-1 infection remains an unmet medical need [64]. Most anti-HIV regimens require daily dosing and cause patients non-compliance and non-adherence to the dosing schedule [44,60,65]. Many anti-HIV drugs have similar chemical structures (NRTI and NNRTI). This structural similarity is a common cause of cross-resistance among these drugs. HIV-1 develops broad multi-class drug resistance due to mutations in HIV-1, non-adherence to the prescribed treatment, and cross-resistance of anti-HIV drugs [36]. This phenomenon is seen in heavily treatment-experienced HIV-1 infected patients and limits the effectiveness of ART [26]. Accordingly, these patients have limited treatment options and are at a higher risk of morbidity and mortality [3]. Long-acting anti-HIV drugs can improve the quality of life of this class of HIV-1 patients and can combat the MDR HIV-1 infection [44]. Accordingly, the scientific fraternity is trying to develop long-acting anti-HIV agents for this class of patients.
LEN is a long-acting and patient compliant (oral/subcutaneous administration and less frequent dosing schedule) first-in-class HIV-1 capsid inhibitor approved by the USFDA, Health Canada, and EMA for the treatment of MDR HIV-1 infection (Table 1) [11][12][13]. LEN demonstrated a low level of drug-related mutations, is active against MDR HIV-1 infection and does not demonstrate cross-resistance to ARTs due to its novel mechanism of action ( Figure 4) [3,66,67]. LEN is also an excellent drug for patients having difficult or limited access to healthcare facilities [68,69]. The long-acting and patient-compliant LEN can address the unmet need of MDR HIV-1, high-risk population of HIV-1, and HIV-1 infected patients with a history of ineffective diverse treatment, drug resistance, and viremia level [13].
HIV-1 variants (Q67H, N74D, and Q67H/N74D) with mutations in the binding sites of LEN have been identified [20,70]. One report established that certain mutations do not affect LEN's in vitro efficacy [71]. Another report states a decrease in the anti-HIV activity of LEN against some variants (M66I, K70H, and Q67H + K70R). The exact effects of these mutilations on the efficacy of LEN are yet to be explored and need further investigations.
HIV-1 is the causative agent for AIDS, which makes them highly susceptible to fatal and opportunistic infections and other diseases, including opportunistic infections such as tuberculosis (TB), hypertension, hepatitis, lipidemia, diabetes, asthma, and mental health issues [72][73][74][75]. The accompanied diseases make HIV treatment complex and warrant drug interaction studies (drug-drug, drug-food, and drug-disease interaction) [69]. Some LENbased drug interaction studies have been performed (Table 3). However, there remain a lot of new drug interaction studies for LEN ( Figure 6). This is one of the interesting areas for scientists to work upon. It is also imperative to note that if LEN therapy is discontinued, it may remain in the patient's systemic circulation for long periods. Therefore, drug interaction must be handled before starting the new anti-HIV treatment [20,24,25]. warrant drug interaction studies (drug-drug, drug-food, and drug-disease interaction) [69]. Some LEN-based drug interaction studies have been performed (Table 3). However, there remain a lot of new drug interaction studies for LEN ( Figure 6). This is one of the interesting areas for scientists to work upon. It is also imperative to note that if LEN therapy is discontinued, it may remain in the patient's systemic circulation for long periods. Therefore, drug interaction must be handled before starting the new anti-HIV treatment [20,24,25]. Monotherapy with an anti-HIV agent provides temporary effects, and soon HIV develops resistance to monotherapy. Accordingly, combination therapy for HIV-1 treatment is recommended [13,60,65,69,76]. Cabenuva (rilpivirine + raltegravir) is the first long-acting FDA-approved therapy for HIV-1 infections [44]. One study has demonstrated the additive/synergistic effects of combining LEN with rilpivirine, cabotegravir, and islatravir [44]. The scientists are also trying to develop a suitable longacting partner for LEN [13]. Some traditional medicines, vitamins, and immunity boosters help treat HIV-1 infection [77,78]. Combining LEN with these supplements may also provide a patient-compliant LEN-based therapy. Monotherapy with an anti-HIV agent provides temporary effects, and soon HIV develops resistance to monotherapy. Accordingly, combination therapy for HIV-1 treatment is recommended [13,60,65,69,76]. Cabenuva (rilpivirine + raltegravir) is the first longacting FDA-approved therapy for HIV-1 infections [44]. One study has demonstrated the additive/synergistic effects of combining LEN with rilpivirine, cabotegravir, and islatravir [44]. The scientists are also trying to develop a suitable long-acting partner for LEN [13]. Some traditional medicines, vitamins, and immunity boosters help treat HIV-1 infection [77,78]. Combining LEN with these supplements may also provide a patientcompliant LEN-based therapy.
The patent literature of LEN reveals its inventions related to compound per se, manufacturing process, crystalline/amorphous polymorphs, method of treating HIV infection, and drug combinations with some drugs/vaccines (islatravir, bictegravir, tenofovir, abacavir, protease inhibitor, NNRTI, NRTI, integrase inhibitor, and pharmacokinetic enhancers) (Table 4). However, most of these patents/applications are silent about the experimental evidence of the claimed inventions. This knowledge gap creates an opportunity to explore this area of HIV-1 treatment. There is also scope for developing more inventions related to new LEN-based regimens with improved treatment outcomes, drug combinations with specific drugs (ART, anti-TB agent, and pharmacokinetic modulators), indications for other viral diseases, dosage forms, analog with anti-HIV activity, co-crystals and salts with improved pharmaceutical properties, economical/simple manufacturing process, and particle size. LEN is a newly approved anti-HIV agent, and LEN-based therapy requires additional monitoring. This step will quickly recognize new safety data. All this additional research may provide more long-acting, potent, non-toxic, stable, and patient-compliant LEN-based treatment with favorable pharmacokinetic parameters for MDR HIV-1 infections and associated opportunistic infections such as TB.

Conclusions
LEN inhibits the HIV-1 replication cycle at different stages due to its unique HIV-1 capsid inhibitory mechanism, making it active against MDR HIV-1 infection. Introducing long-acting and patient-compliant LEN therapy with no known cross-resistance and drug resistance brings new hope for MDR HIV-1 infected patients. The patented long-acting LEN-based combination therapies with islatravir, bictegravir, and tenofovir are in the clinical trial. The authors foresee the possibility of developing many LEN combinations with existing ARTs for HIV-1 infection treatment. Opportunistic infections such as TB accompany AIDS. Therefore, the drug-drug interaction-based combination therapy of LEN and anti-TB drugs also need investigations. The marketing approval of LEN is a milestone for HIV-1-infected patients, and it would be interesting to see the development of several advantageous LEN-based therapies for MDR HIV-1 infection.