The present invention relates to a novel Pleuromutilin and novel therapeutic use of Pleuromutilins.

Pleuromutilin, a compound of formula is a naturally occurring antibiotic, produced e.g. by the basidiomycetes Pleurotus mutilus and P. passeckerianus, see e.g. The Merck Index, 12th edition, item 7694.

A number of further pleuromutilins having the principle ring structure of pleuromutilin and being substituted at the primary hydroxy group have been developed, e.g. as antibacterials. Due to their pronounced antibacterial activity, a group of pleuromutilin derivatives, amino- hydroxy-substituted cyclohexyl sulfanylacetylmutilins, as disclosed in WO 2008/113089, have been found to be of particular interest. As described in W 02008/113089 14-0- {[(4- Amino-2-hydroxy-cyclohexyl)-sulfanyl]-acetyl}-mutilins are particularly useful compounds because of their activity against Gram-positive and Gram-negative bacteria.

In WO 2015/110481 A1 Pleuromutilin derivatives are disclosed which are called “12-epi- mutilins”. The term “12-epi-mutilin” means that the mutilin ring at position 12 is substituted by two substituents, the first substituent at position 12 of the mutilin ring is a methyl group which methyl group has the inverse stereochemistry compared with the stereochemistry of the methyl group at position 12 of the naturally occurring pleuromutilin ring, the second substituent at position 12 of the mutilin ring is a hydrocarbon group comprising at least one nitrogen atom, and all other substituents of the mutilin ring having the same stereochemistry compared with the stereochemistry of the substituents at the corresponding positions in the naturally occurring pleuromutilin ring; optionally in the form of a salt and/or solvate, in particular in the form of a salt. A first synthetic approach towards the inverted stereochemistry was described by Berner, H. et al (Berner, H.; Schulz, G.; Schneider H. Tetrahedron 1980, 36, 1807-1811).

In WO 2015/110481 Al, certain of these 12-epi-mutilin compounds have been found to show interesting activity against Gram-positive and Gram-negative bacteria.

Pharmaceutical active compounds derived from pleuromutilin (semi synthetic compounds) are inhibitors of ribosomal protein synthesis in bacteria. Representatives of semisynthetic pleuromutilins for human use are Retapamulin (approved as AltargoP ^® , AltabaxP ^® ), a topical agent approved for short term treatment of impetigo and infected small lacerations, abrasions or sutured wounds, and Lefamulin (approved as Xenleta ^® ) for the treatment of adults with community-acquired bacterial pneumonia (CABP). Tiamulin (Denagard ^® ) and Valnemulin (Econor ^® ) are two other semi-synthetic pleuromutilin derivatives which have been used systemically as antibiotics in veterinary medicine for many years.

Approved semisynthetic compounds derived from pleuromutilin have shown excellent activity against bacterial organisms which include inter alia Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus (including MRS A), Moraxella catarrhalis, Legionella pneumophila, Chlamydophila pneumoniae and Mycoplasma pneumoniae.

Viral diseases are one of the leading causes of morbidity and mortality in the world. Respiratory viruses such as influenza, respiratory syncytial virus, certain adenoviruses, rhinoviruses and corona viruses and in particular the newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; COVID-19) have a significant impact on public health.

In Asheshov, Igor N. et. al., Antibiotics & Chemotherapy 4/4 (1954), 380-394, for the first time the antiviral activity of pleuromutilins was described with antiviral activity of Pleuromutilin itself for an influenza A virus strain (PR8) at a concentration of 2 mg/mL. In contrast, Pleuromutilin did not show antiviral activity for polio virus in this study.

Furthermore, in Alacom, Balbino et.al., Antiviral Research, 4 (1984), 231-243, the antiviral activity of Pleuromutilin against both, DNA and RNA viruses, in particular herpes simplex type 1 (HSV-1) virus at a test compound concentration that conferred a 50% protection of the cytopathic effect induced by HSV-1 (CPE50) of 40 mM (15 pg/mL) and activity against vesicular stomatitis virus (VSV) is described.

In WO 2009/106839 the use of Tiamulin as an antiviral agent is claimed, with effect of Tiamulin on influenza A virus, porcine reproductive and respiratory syndrome virus (PRRSV) type 1 and 2 in a viral up-take assay 4 hours post inoculation with the virus at tiamulin concentrations of 0.1-10 pg/mL compared to Valnemulin and the effect of Tiamulin on endosomal pH exemplified. Valnemulin did not exhibit antiviral activity and it was stated that other pleuromutilin antibiotics have not been found to have an effect on viruses.

Alteration of the endosomal or lysosomal pH by Tiamulin and associated prevention of fusion of the viral membrane with endo- and lysosomes, which is a pre-requisite for viral entry, was described as potential mode-of-action.

CN 103204787B and CN 103242210 both disclose further pleuromutilin derivatives and generally mention their use in antiviral drugs, without, however, disclosing any actual proof for an antiviral action.

Certain statements about potential antiviral and anti-inflammatory effects of Lefamulin were made in the “Q1 2020 Nabriva Therapeutics PLC Earnings Call” of May 11, 2020, (a transcript of which is available under https://www.yahoo.com/news/edited-transcript-nbrv- oq-eamings-144108621.html, downloaded June 10, 2020 as well as in a press release of May 11, 2020 (https://investors.nabriva.com/news-releases/news-release-de tails/nabriva- therapeutics-reports-first-quarter-2020-fmancial), downloaded May 28, 2020. SUMMARY OF THE INVENTION

Surprisingly, it was now found that the 12-epi mutilins as disclosed in WO 2015/110481 A1 are effective against viruses and, thus, effective against diseases mediated by viruses.

Therefore, in a first aspect the present invention relates to a compound as defined in claims 1 to 11 and 16, or a pharmaceutically acceptable salt, solvate, prodrug or metabolite thereof, for the specific use in the treatment or prevention of a disease mediated by a virus.

In a further aspect, the present invention relates to a method of treatment or prevention of a disease mediated by a virus, comprising administering a compound as defined in any of claims 1 to 11 and 16, or a pharmaceutically acceptable salt, solvate, prodrug or metabolite thereof to a subj ect in need of such treatment.

In yet a further aspect, the present invention relates to the compound of claims 11 and 16, respectively and to its use as a medicament as well as a specific use in the treatment of a disease mediated by bacteria, in particular Gram positive bacteria, and/or a disease mediated by a virus.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 demonstrates the effect of the compound of claim 16 (BC-9842) against alpha corona virus 229E (HCoV-229E) in MRC-5 cells 6 days post infections with the virus.

Figure 2 demonstrates the effect of Tiamulin in the same assay.

Figure 3 demonstrates the effect of Remdesivir in the same assay.

Figure 4 demonstrates the effect of the compound of claim 16 (BC-9842) against respiratory syncytial virus type A in HEp2 cells 6 days post infections with the virus.

Figure 5 demonstrates the effect of Tiamulin in the same assay.

Figure 6 demonstrates the effect of TMC353121 in the same assay.

DETAILED DESCRIPTION OF THE INVENTION

The present invention refers to the treatment and prevention of a disease mediated by a virus, e.g. a viral disease or a viral infection. Treatment typically includes administering a compound as used according to the present invention to a subject in need thereof, i.e. a subject being diagnosed to have a disease mediated by a virus. Prevention of a disease mediated by a virus includes administering the compounds before onset of disease symptoms. Prevention may be considered after a subject has been infected with a virus but has not shown any symptoms, or wherein a subject has been exposed and/or is prone to exposition to a virus.

The results of the experiments show that besides its antibacterial activity, the 12-epi-mutilin BC-9842 is also actively reducing the cytopathic effect mediated by different viruses. This antiviral effect was particularly shown for such viruses that are characterized in that they are positive- or negative sense single-stranded RNA viruses, in particular, enveloped positive- or negative sense single-stranded RNA viruses (such as Coronaviridae, Paramyxoviridae, Orthomyxoviridae, and Flaviviridae). Moreover, some of the investigated viruses, including measles virus are known for a transmission involving the respiratory route, in particular airborne transmission. Corona virus and Respiratory Syncytial Virus also cause infections of the respiratory tract in humans.

In a preferred embodiment of the present invention, the virus is a positive- or negative-sense single-stranded RNA virus, preferably the virus is selected from the group consisting of

Coronaviridae including in particular human coronavirus,

Paramyxoviridae including in particular Paramyxovirinae, such as Measles virus, and Pneumovirinae, such as Respiratory Syncytial Virus,

Orthomyxoviridae including in particular Influenza virus,

Flaviviridae including in particular Dengue virus and Zika virus, and Picornaviridae including in particular Rhinovirus.

In an other embodiment, the disease is an airborne disease. An airborne disease is mediated by a virus transmitted by the air.

Viral infections can affect various organs. In a preferred embodiment of the present invention, the disease is a respiratory disease, including upper and lower respiratory infections, in particular lower respiratory infections.

In particular, the disease is an acute respiratory syndrome, such as Influenza, Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS) or COVID-19.

In a further embodiment of the present invention the disease is mediated by a virus selected from the group consisting of viruses of the virus families Coronaviridae, in particular a corona virus such as SARS-CoV, SARS-CoV2, MERS-CoV or HCoV-229E, Orthomyxoviridae, in particular an Influenza virus such as Influenza A and B viruses, Paramyxoviridae in particular Respiratory Syncytial Virus and Adenoviridae, in particular Adenovirus.

In one embodiment, the virus is a corona virus, in particular selected from the group consisting of SARS-CoV, SARS-CoV2, MERS-CoV, and HCoV-229E as well as mutations thereof. Such corona viruses are known to cause (severe) acute respiratory syndromes, such as SARS, MERS or COVID-19.

The compounds used according to the present invention are generally known from WO 2015/110481 Al, the disclosure of which is incorporated herein by reference. Especially the compounds used according to the present invention can be synthesized according to the preparation methods disclosed in WO 2015/110481 Al. Alternatively, a synthetic approach via 14-0-chloroacetyl-12-epi-mutilin is available as described in the co-pending application (PCT/EP2021/059885).

In a further aspect, the present invention relates to a novel 12-epi-mutilin of formula II optionally in form of a pharmaceutically acceptable salt, in particular the dihydrochloride salt and/or solvate.

The systematic name of this compound is 12-epi-12-desvinyl-14-0-[(Piperidin-4- ylsulfanyl]-acetyl]-12-[2-(3-methyl-pyrazin-2-yl)-ethenyl]-m utilin. In the following, this compound is also referred to as “BC-9842”.

This compound is novel and has surprisingly good efficacy both against the microbes as generally disclosed in WO 2015/110481 (MICs < 2 pg/mL against Staphylococcus aureus ATCCC 49951 and MICs < 16 pg/mL against Escherichia coli ATCC 25922) and against viruses (Examples 2 to 5). In particular, BC-9842 has a MIC (minimum inhibitory concentration) of < 0.03pg/mL against Staphylococcus aureus ATCC49951 and Streptococcus pneumoniae ATCC49619 (Example 6). Moreover, BC-9842 has shown good metabolic stability in mouse and human primary hepatocytes e.g. of > 60% and of > 20% parent compound, respectively (Example 7).

Thus, the invention also relates to BC-9842, optionally in the form of a pharmaceutically acceptable salt, for use as a medicament.

In a further aspect, the present invention provides BC-9842 for use in the treatment and prevention of a disease mediated by bacteria.

In one embodiment, the disease is mediated by bacteria selected from the group consisting of

- Gram-positive bacteria including

• staphylococci, e.g. Staphylococcus aureus ,

• streptococci, e.g. Streptococcus pneumoniae , B-hemolytic or viridans group Streptococcus spp.

• enterococci, e.g. Enterococcus faecium,

• Peptostreptococci, e.g. Peptostreptococcus anaerobius,

• Clostridia, e.g. Clostridium difficile and Clostridium perfringens ,

• as well as Listeria monocytogenes , Eubacterium lentum , Finegoldia magna , Anaerococcus prevotii , Peptoniphilus assaccharolyticus, and Propionibacterium spp. and

- Gram-negative bacteria including

• Moraxella, e.g. Moraxella catarrhalis ,

• Haemophilus, e.g. Haemophilus influenzae and Haemophilus parainfluenzeae,

• Chlamydiae, e.g. Chlamydophila pneumoniae and Chlamydia trachomatis

• Neisseriaceae, e.g. Neisseria gonorrhoeae,

• Mycoplasma spp., e.g. Mycoplasma pneumoniae and Mycoplasma genitalium,

• Fusobacteria, e.g. Fusobacterium fusiforme , Fusobacterium necrophorum, Fusobacterium mortiferum, and Fusobacterium varium ,

• Prevotella spp., e.g. Prevotella buccae and Prevotella oris

• Porphyromonas spp., e.g. Porphyromonas gingivalis and Porphyromonas asaccharolytica,

• Legionella, e.g. Legionella pneumophila

• as well as Bacteroides fragilis , and Acinetobacter Iwoffii. The disease may be mediated by Gram-negative or Gram-positive bacteria including aerobes, facultative anaerobes or obligatory anaerobes. In one embodiment, the disease is mediated by aerobic or facultative anaerobic bacteria, in particular aerobic or facultative anaerobic Gram-positive bacteria.

Preferably, the disease is mediated by bacteria selected from the group consisting of staphylococci and streptococci.

Individual bacterial phenotypes with resistance against pleuromutilin antibiotics (Long, K.

S.; Poehlsgaard, J.; Kehrenberg, C.; Schwarz, S.; Vester, B. Antimicrob Agents Chemother. 2006, 50(7), 2500-2505) and Lefamulin (Mendes RE, Paukner S, Doyle TB, Gelone SP, Flamm RK, Sader HS. Antimicrob Agents Chemother. 2019 63(4), e02158-18; ) have been described. Potential acquired Lefamulin resistance mechanisms identified to date include the following (sorted by epidemiological relevance): i) target protection by ABC-F proteins e.g. vgar(A-E) of Staphylococcus spp., lsa( E) of S. agalactiae, Enterococcus spp., and S. aureus, sal( A) of coagulase-negative Staphylococcus spp., ii) Modification of the target e.g. Mutations in rplC and rplD genes encoding ribosomal proteins located outside of PTC, mutations in domain V of the 23 S rRNA, or methylation of position A2503 of the 23 S rRNAin the PTC mediated by the Cfr methyl transferase (encoded by cfr) (Paukner S, Riedl R. Pleuromutilins: Potent Drugs for Resistant Bugs-Mode of Action and Resistance. Cold Spring Harb Perspect Med. 2017 Jan 3;7(l):a027110. doi: 10.1101/cshperspect.a027110. PMID: 27742734; PMCID: PMC5204327).

In particular, the disease is mediated by bacteria resistant to Lefamulin. For example, bacteria having a resistance mechanism, e.g. mediated by vga(A), lsa( E) or cfr.

In a preferred embodiment, the disease is selected from the group consisting of a respiratory tract infection including pneumonia, e.g. a community-acquired bacterial pneumonia (CABP) and nosocomial pneumonia, an infection of skin and/or soft tissue including acute bacterial skin and skin structure infection (ABSSI), a systemic infection including sepsis, a prosthetic j oint infection, sexually transmitted infections (STI) and acne. More preferably, the disease is a respiratory tract infection including community-acquired pneumonia and nosocomial pneumonia, a skin and/or soft tissue infection including acute bacterial skin and skin structure infection, a sexually transmitted infection, or sepsis.

Moreover, the present invention relates to a method of treatment or prevention of a disease mediated by bacteria, comprising administering BC-9842 or a pharmaceutically acceptable salt, solvate, prodrug or metabolite thereof to a subject in need of such treatment.

Furthermore, the invention also relates to a pharmaceutical composition comprising BC-9842 optionally in the form of a pharmaceutically acceptable salt, in association with at least one pharmaceutical excipient, optionally further comprising another pharmaceutically active agent.

Treating, treatment or to treat as understood herein includes on one hand the complete curing, curation or to cure a condition (the infectious disease) such that it comes to its end and on the other hand also ameliorating, amelioration or to ameliorate a condition such that its symptoms are reduced at least partially or individually.

Preventing, prevention, or to prevent includes administering a compound before a condition is diagnosed or before onset of (all) disease symptoms of the condition. For example, prevention according to the present invention may be considered after a subject has been infected with a virus and/or bacteria but has not shown any symptoms of an infection (asymptomatic carrier) or, wherein a subject has been exposed and/or is prone to exposition to a virus and/or bacteria known for mediating, i.e. causing, a certain infectious disease. In one embodiment, the compound to be used according to the invention, in particlar BC-9842 is administered to treat a viral infection itself and to prevent a co- and/or superinfection mediated by bacteria.

The appropriate dosage of the compound to be used according to the present invention, in particular BC-9842, will, of course, vary depending upon, for example, the individual host, the mode of administration and the nature and severity of the conditions being treated. However, in general, for satisfactory results in larger mammals, for example humans, an indicated daily dosage is in the range from about 0.5 mg to 3 g of a compound of the present invention or for use as to the present invention conveniently administered, for example, in divided doses up to four times a day. The compound used according to the present invention may be administered by any conventional route, for example enterally, e.g. including nasal, buccal, rectal, oral administration; parenterally, e.g. including intravenous, intramuscular, subcutaneous administration; or topically, e.g. including pulmonary, epicutaneous, intranasal, intratracheal administration, e.g. in form of coated or uncoated tablets, capsules, injectable solutions or suspensions, e.g. in the form of ampoules, vials, in the form of ointments, creams, gels, pastes, inhaler powder, foams, tinctures, lip sticks, drops, sprays, or in the form of suppositories, e.g. in analogous manner to the antibiotic agent tobramycin or macrolides, such as erythromycins, e.g. clarithromycin or azithromycin.

Preferably, the compound used according to the present invention is administered via inhalation, via intravenous or subcutaneous injection, or orally.

The compound for use according to the present invention, in particular BC-9842, is in the free form or a pharmaceutically acceptable salt, solvate, prodrug or metabolite thereof. Preferably, the compound for use according to the present invention is in the free form, as defined by formula I or II, in the form of a pharmaceutically acceptable salt and/or in the form of a solvate.

The compound used according to the present invention, in particular BC-9842, may be administered in the form of a pharmaceutically acceptable salt, e.g. an acid addition salt, or in free form, optionally in the form of a solvate.

A salt of a compound used according to the present invention includes an acid addition salt. Pharmaceutically acceptable acid addition salts include salts of a compound of the present invention or used according to the present invention with an acid, e.g. hydrogen fumaric acid, fumaric acid, tartaric acid, ethane- 1,2-disulphonic acid, maleic acid, naphthalin-1,5- sulphonic acid, acetic acid, malic acid, lactic acid e.g. L-lactic acid, succinic acid, salicylic acid, azelaic acid, 2-[(2,6-dichlorophenyl)amino]benzene acetic acid, hydrochloric acid, deuterochloric acid, preferably hydrochloric acid, acetic acid, L-lactic acid and maleic acid, more preferably hydrochloric acid.

In a preferred embodiment, BC-9842 is provided in the form of its dihydrochloride salt.

The compound used according to the present invention, in particular BC-9842, may be used for the pharmaceutical treatment contemplated herein alone or in combination with one or more other pharmaceutically active agents. Such other pharmaceutically active agents include e.g. other antiviral agents. Such other antiviral agents may preferably be selected from the group consisting of nucleoside and nucleotide analogues and RNA polymerase inhibitors, e.g. remdesivir or ribavirin, viral protease inhibitors such as lopinavir or ritonavir, viral neuraminidase inhibitors, such as oseltamivir, and other agents used in antiviral therapy such as hydroxychloroquine, interferons (interferon alfa and/or beta), or other broad- spectrum antiviral agents.

In one embodiment, BC-9842 may be used for pharmaceutical treatment according to the present invention alone or in combination with one or more other pharmaceutically active agents. Such other pharmaceutically active agents include e.g. other antibiotics and anti inflammatory agents, and, if used in the treatment of acne, other pharmaceutically agents include furthermore agents which are active against acne.

Combinations include fixed combinations, in which two or more pharmaceutically active agents are in the same formulation; kits, in which two or more pharmaceutically active agents in separate formulations are sold in the same package, e.g. with instruction for co administration; and free combinations in which the pharmaceutically active agents are packaged separately, but instruction for simultaneous or sequential administration are given.

A pharmaceutical composition comprising a compound used according to the present invention, in particular BC-9842, may in addition comprise at least one pharmaceutically acceptable excipient, e.g. carrier or diluent, e.g. including fillers, binders, disintegrators, flow conditioners, lubricants, sugars and sweeteners, fragrances, preservatives, stabilizers, wetting agents and/or emulsifiers, solubilizers, salts for regulating osmotic pressure and/or buffers.

Such pharmaceutical compositions may be manufactured according, e.g. analogously, to a method as conventional, e.g. by mixing, granulating, coating, dissolving, spray drying or lyophilizing processes. Unit dosage form may contain, for example, from about 0.5 mg to about 3000 mg, such as 10 mg to about 600 mg.

A subject in need of a treatment as contemplated by the present invention may be any living subject suffering from a disease mediated by a virus, i.e. a viral infection, and/or in case of the use of BC-9842 suffering from a disease mediated by bacteria, i.e. a bacterial infection. Especially, the subject may be a human or an animal. Examples

The trivial name mutilin refers to the IUPAC systematic name (IS, 2R, 3S, 4S, 6R, 7R, 8R, 14R)-3,6-dihydroxy-2,4,7,14-tetramethyl-4-vinyl-tricyclo[5.4 .3.0 ^1,8 ]tetradecan-9-one.

In the following examples, pleuromutilin derivatives are numbered in analogy to the mutilin numbering system described by H. Berner (Berner, H.; Schulz, G.; Schneider H. Tetrahedron 1980,

In the compounds of the present invention, e.g. in the compounds of example 1, the stereochemistry of the methyl group at position 12 (and in turn also the stereochemistry of the second group attached in position 12 of the mutilin ring) is inverted (epi-mutilin derivatives) and in addition the vinyl group is altered and various substituents instead of vinyl have been introduced: 12-Epi-pleuromutilin and 12-epi-pleuromutilin tosylate are compounds of formulae: respectively.

Herein, including the examples and the reaction scheme the following abbreviations are used:

¹ H-NMR proton nuclear magnetic resonance spectroscopy

°C degrees Celsius mM micromolar concentration

BC-9842 12-epi-12-desvinyl-14-0-[(Piperidin-4-ylsulfanyl]-acetyl]-12 -[2-(3-methyl- pyrazin-2-yl)-ethenyl]-mutilin

BOC tert-butyl oxy carb ony

CoV corona virus

CPE cytopathic effects, in particular virus-induced

DMEM Dulbecco's modified Eagle's medium

EC50 Half maximal (fifty-percent) effective concentration

EtOAc ethyl acetate

FBS Fetal bovine serum

HeLa immortal human epithelial cell line

HEp2 human epithelial cell line

M molarity m/z mass/charge ratio

MOI Multiplicity of infection

MRC-5 Medical Research Council cell strain 5

MS mass spectrometry nm nanometer

TC50 Half maximal (fifty-percent) toxic concentration

TCID50 Fifty-percent (half maximal) tissue culture infective dose

XTT 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-c arboxanilide Example 1: Preparation of BC-9842

12-epi-12-Desvinyl-14-0-[(Piperidin-4-ylsulfanyl)-acetyl] -12-[(E)-2-(3-methyl-pyrazin- 2-yl)-vinyl]-mutilin dihydrochloride

Step 1 : 12-epi-14-0-rn-tert-Butoxycarbonyl-piperidine-4-ylsulfanvD-a cetyl1-mutilin

To 12-epi-Pleuromutilintosylate (37.2 g) was added methanol (200 mL), tert-butyl 4- acetylsulfanylpiperidine-l-carboxylate (18.1 g) as well as potassium carbonate solution (5M in water, 55.9 mL) and sonicated for 1.5 hours in an ultrasonic bath at room temperature.

The resulting solution was concentrated to dryness, taken up in ethyl acetate and washed twice with half-saturated NaCl solution. The organic phase was dried over anhydrous Na2SC>4 and evaporated to dryness under reduced pressure to obtain the title compound (quantitative yield containing residual solvent) in the form of a pale-yellow to yellow solid. The crude product is used for the next step without further purification.

1H-NMR (400 MHz, CDC13, d, ppm, characteristic signals, mutilin numbering system): 5.74-5.62 (m, 1 H, H-19), 5.56 (d, 1H, H-14, J=8.0 Hz), 5.20-5.07 (m, 2H, H-20), 4.01-3.80 (m, 2H, H-22), 3.37 (d, 1H, H-ll, J=6.0Hz), 1.39 (m, 12H, BOC, CH ₃ -15), 1.15 (s, 3H, CH ₃ - 18), 0.89 (d, 3H, CH ₃ -17, J=6.8 Hz), 0.66 (d, 3H, CH ₃ -16, J=6.8 Hz).

MS m/z: 612 [M + CT], 622 [M + HCOO ].

Step 2: 12-epi-12-desvinyl-14-0-r(T-tert-Butoxycarbonyl-piperidin-4- ylsulfanvD-acetvn-12- r2-(3-methyl-pyrazin-2-vD-ethenvn-mutilin

2-Bromo-3-methylpyrazine (95%, 5.99 g) and bis-(benzonitrile)-palladium(II)-chlorid (2.66 g) were suspended in ethylene glycol (400 mL). Then 12-epi-14-0-[(l-tert-Butoxycarbonyl- piperidine-4-ylsulfanyl)-acetyl]-mutilin (10 g), N-methyl-morpholine (15.22 mL) and ethylene glycol (600 mL) were added subsequently to give an orange suspension. The resulting mixture was stirred at 110°C overnight. The reaction mixture was diluted with ethyl acetate, extracted with 0.05M HCl/NaCl solution (500 mL, 0.1 M aqueous HC1 + 5% aqueous NaCl solution, 1:1) and twice with 5% aqueous NaCl solution. The aqueous phases were washed with ethyl acetate. All organic phases were combined, washed with saturated aqueous NaCl solution, dried over anhydrous NaiSCL and concentrated under reduced pressure. The evaporation residue was subjected to chromatography over silica gel using cyclohexane / EtOAc 1 : 10 and EtOAc as eluents to obtain the title compound (1.39 g) as a pale-yellow to yellow solid. 'H-NMR (400 MHz, CDC13, d, ppm, characteristic signals, mutilin numbering system): 8.29-8.23 (m, 2H, aromat.), 6.86 and 6.64 (2d, 2 H, H-19, H-20, J=15.4 Hz), 5.59 (d, 1H, H- 14, J=8.4 Hz), 4.00-3.80 (m, 2H, H-22), 3.60 (d, 1H, H-l l, J=6.4Hz), 2.55 (s, 3H, CH ₃ - aromat.), 1.42-1.32 (m, 15H, BOC, CH ₃ -15, CH ₃ -I8), 0.91 (d, 3H, CH ₃ -17, J=6.8 Hz), 0.68 (d, 3H, CH ₃ -I6, J=6.8 Hz).

MS m/z: 670 [M + H ⁺ ], 714 [M + HCOO ].

Step 3: 12-epi-12-desvinyl-14-0-r(Piperidin-4-ylsulfanyl1-acetyl1-12 -r2-(3-methyl-pyrazin-

2-vD-ethenyll -mutilin dihydrochl pride

12-epi-12-desvinyl-14-0-[(l-tert-Butoxycarbonyl-piperidin -4-ylsulfanyl)-acetyl]-12-[2-(3- methyl-pyrazin-2-yl)-ethenyl]-mutilin (1.39 g) was dissolved in dichloromethane and trifluoroacetic acid (10 mL) was added. The reaction mixture was stirred for 30 minutes at room temperature and evaporated to dryness. The resulting residual was dissolved in dichloromethane and hydrogen chlorid (2M in diethyl ether, 10 mL) was added. The resulting mixture was evaporated again to dryness and the resulting residual was dissolved in water, washed three times with diethylether and lyophilized to obtain the title compound (925 mg) as an orange solid.

Ή-NMEI (400 MHz, DMSO-d6, d, ppm, characteristic signals, mutilin numbering system): 9.40-9.05 (m, 2H, NH ₂ ), 8.50-8.32 (m, 2H, aromat.), 7.15 and 6.53 (2d, 2H, H-19, H-20, J = 16 Hz), 5.57 (d, 1H, H-14, J = 7.6 Hz), 3.76-3.67 (m, 1H, H-l l), 2.57 (s, 3H, CH ₃ -aromat.), 1.40 (s, 3H, H-15), 1.23 (s, 3H, H-18), 0.88 (d, 3H, H-17, J = 6.4Hz), 0.67 (d, 3H, H-16, J = 6.0 Hz).

MS m/z: 570 [M + H ⁺ ], 604 [M + Cl ].

Example 2: Anti-Coronavirus Cytoprotection Assay

Objective: The assay measured the inhibition of virus-induced cytopathic effects (CPE) and cell viability following alpha coronavirus 229E (HCoV-229E or C0V _229E ) in MRC-5 cells 6 days post infections with the virus by various concentrations of the investigated compounds.

Methodology: MRC-5 cells were seeded in 96-well flat-bottom tissue culture plates (at a density of 3 x 10 ³ cells per well) and allowed to adhere overnight. Thereafter, diluted test compounds (BC-9842 as dihydrochloride, Tiamulin as fumarate) in DMSO were added to the plate and incubated for 4 hours prior to addition of the virus. The virus was added diluted to a pre-determined titer to yield 85-95% cell killing at 6 days post-infection (MOI of 0.001).

Following incubation at 37°C and at 5% CO ₂ for 6 days, cell viability was measured by XTT tetrazolium dye staining. The optical density of the cell culture plate was determined spectrophotometrically at 450 and 650 nm. Percent reduction of the virus-infected cells and the percent cell viability of uninfected drug control wells were calculated to determine the effective concentration at which 50% of cytopathic effect was inhibited (EC ₅₀ ) and the cytotoxic concentration (TC ₅₀ ) using four parameter curve fit analysis. The antiviral compound Remdesivir served as positive control.

Results:

Surprisingly, BC-9842 reduced the viral CPE by 100% at concentrations of 5 mM and 10 pM, which are concentrations that had no cytotoxic effect on the viability of the cell control. The calculated EC50 was 1.92 pM, at which 50% of the viral cytopathic effect was inhibited. At the BC-9842 concentration of 50 pM, BC-9842 displayed a cytotoxic effect; the calculated TC50 was 22.4 pM. The ratio of EC50 and TC50, known also as therapeutic index, was 11.7.

In contrast, Tiamulin at a concentration of 10 pM reduced the viral CPE only by 10.53% and no cytotoxic effect was observed. At the next higher test concentration of 50 pM the CPE was reduced by 81.68% and a cytotoxic effect was observed. The calculated EC50 was 24.4 pM and the calculated TC50 was 62.9 pM. The therapeutic index of Tiamulin was 2.58 and surprisingly much lower than that of BC-9842.

The antiviral compound Remdesivir was developed as a treatment for Ebola virus, and also is known to have antiviral activity against corona viruses (clinical investigation is ongoing). Thus, Remdesivir served as positive control herein. Remdesivir showed an EC ₅₀ of 0.11 pM, a TC ₅₀ of > 5 and a therapeutic index of >45.5. The results are graphically displayed in Figures 1 (BC-9842), 2 (Tiamulin) and 3 (Remdesivir) (VC....reduction of viral CPE, CC . Cell Control).

Example 3: Anti-Respiratory Syncytial Virus (RSV) Cytoprotection Assay

Objective: The assay measured the inhibition of virus-induced cytopathic effects (CPE) and cell viability following human respiratory syncytial virus (strain RSV _A 2) replication in HEp2 cells 6 days post infections with the virus by various concentrations of BC-9842.

Methodology: HEp2 cells were seeded in 96-well flat-bottom tissue culture plates (at a density of 5 x 10 ³ cells per well) and allowed to adhere overnight. Thereafter, diluted test compounds (BC-9842 as dihydrochloride, Tiamulin as fumarate) in DMSO were added to the plate and incubated for 4 hours prior to addition of the virus. The virus was added diluted to a pre-determined titer to yield 85-95% cell killing at 6 days post-infection (MOI of 0.001).

Following incubation at 37°C and at 5% CO2 for 6 days, cell viability was measured by XTT tetrazolium dye staining. The optical density of the cell culture plate was determined spectrophotometrically at 450 and 650 nm. Percent reduction of the virus-infected cells and the percent cell viability of uninfected drug control wells were calculated to determine the effective concentration at which 50% of cytopathic effect was inhibited (EC50) and the cytotoxic concentration (TC50) using four parameter curve fit analysis. The antiviral compound TMC353121 (RSV fusion inhibitor) served as positive control.

Results:

Surprisingly, BC-9842 reduced the viral cytopathic effect (CPE) by 52.85% and 69.33% at concentrations of 5 mM and 10 pM, respectively, which are concentrations that had no cytotoxic effect on the viability of the cell control. The calculated EC50 was 4.58 pM, at which 50% of the viral CPE was inhibited. At the BC-9842 concentration of 50 pM, BC-9842 displayed a cytotoxic effect; the calculated TC50 was 22.4 pM. The ratio of EC50 and TC50, known also as therapeutic index, was 4.89.

In contrast, Tiamulin at a concentration of 10 pM reduced the viral CPE only by only 16.76% and a cytotoxic effect (84% viability) was observed at this concentration. At the next higher test concentration of 50 pM the viral CPE was reduced by 43.28% and at the cytotoxic effect was more pronounced (70.0% viability). The calculated EC ₅₀ was with >67.9 pM above the calculated TC ₅₀ of 67.9 pM. The therapeutic index of Tiamulin therefore could not be calculated. Surprisingly, the antiviral activity and therapeutic index was much higher for BC-9842 than for Tiamulin.

The antiviral compound TMC353121 was developed as a specific respiratory syncytial virus fusion inhibitor (clinical investigation is ongoing). Thus, TMC353121 served as positive control herein. TMC353121 showed an EC50 of 0.006 mM, a TC50 of > 0.1 pM and a therapeutic index of > 167.

The results are graphically displayed in Figures 4 (BC-9842), 5 (Tiamulin) and 6 (TMC353121) (VC....reduction of viral CPE, CC . Cell Control).

Example 4: Anti-Respiratory Syncytial Virus (RSV) Cytoprotection Assay using different RSV strains

Objective: The assay measured the inhibition of virus-induced cytopathic effects (CPE) and cell viability following replication of the two different respiratory syncytial virus strains RSV ALONG and RSV B ₁₈₅₃₇ in HEp2 cells.

Methodology: The assay was performed in analogy to Example 3 above with the difference that cells seeded with a density of 5 x 10 ³ cells per well were incubated with the virus strains RSV ALONG or RSV B ₁₈₅₃₇ , respectively, following a 4 hour cell pretreatment with the test compound at different concentrations. Virus was diluted and added in an amount yielding an MOI of 0.01 and 0.001 for RSV ALONG and RSV B18537, respectively.

Results:

The antiviral efficacy and cellular toxicity data are summarized in the tables below. The control compound TMC353121 was evaluated in parallel to BC-9842 and yielded an EC ₅₀ value of 0.01 nM against the investigated strains of RSV A and RSV B. BC-9842 yielded an EC50 values of 6.77 mM against the RSV B18537. Activity against RSV ALONG could not be determined due to the cytotoxicity to HEp2 cells with TC ₅₀ values of 22.4 mM in the assay.

Example 5: Anti-Measles Virus (RSV) Cytoprotection Assay

Objective: The assay measured the inhibition of virus-induced cytopathic effects (CPE) and cell viability during replication of Measles virus strain Edmonston in HeLa cells.

Method: HeLa cells were seeded in 96-well flat-bottom tissue culture plates (at a density of 5 x 10 ³ cells per well) and allowed to adhere overnight. Thereafter, diluted test compounds (BC-9842 as dihydrochloride, Ribavirin for control) were added to the plate and incubated for 4 hours prior to addition of the virus. Virus was added diluted to a pre-determined titer to yield 85-95% cell killing at 6 days post-infection (1:50 dilution, MOI of 0.008).

Cell viability determination and calculation of EC ₅₀ and TC ₅₀ were performed as described in Examples 2 and 3.

Results:

The antiviral efficacy and cellular toxicity data are summarized in the Table below.

Ribavirin was evaluated as control compound in parallel to BC-9842 and yielded an EC50 value of 1.88 pg/mL. BC-9842 reduced the viral CPE by 69 % at a concentration of 10 mM and an EC50 value of 5.36 mM was calculated.

Example 6: Antibacterial activity of BC-9842

The in vitro activity against bacteria including isolates that are resistant to Lefamulin was determined by standard broth microdilution according to the Clinical and Laboratory Standards Institute CLSI document (Performance Standards for Antimicrobial Susceptibility Testing) M100Ed29E (2019) and (Methods for Dilution Antimicrobial Susceptibility Test for Bacteria That Grow Aerobically) M07Edl 1 (2018) or other years’ versions thereof. The data were obtained using cation-adjusted Mueller Hinton broth medium (CAMHB).

Results for BC-9842 in comparison to Example 154 of WO 2015/110481 A1 (12-epi-12- desvinyl-14-0-[(azepan-4-ylsulfanyl)-acetyl]-12-((E)-2-pyrid in-3-yl-ethenyl) mutilin hydrochloride) and Lefamulin are summarized in the table below.

BC-9842 exhibits MICs < 0.1 pg/ml against Staphylococcus aureus ATCC49951, and Streptococcus pneumoniae ATCC49619. In addition, BC-9842 exhibits MICs < 4 pg/ml against Lefamulin resistant Staphylococcus aureus strains mediated by e.g. cfr or vga( A) and Lefamulin resistant Streptococcus agalactiae strains mediated by e.g. lsa E) resistance mechanisms.

Example 7: Metabolic stability of BC-9842

The metabolic stability of BC-9842 was determined by using cryopreserved primary mouse or human hepatocytes. About 1.00 x 10 ⁵ cells/mL in Krebs-Henseleit buffer (KHB) were incubated in the absence and the presence of 1 pg/mL of the test compounds at 37°C, 5% CO2 for 4 hours (in triplicate). Test compounds were dissolved in dimethyl sulfoxide (DMSO) and further diluted with KHB, so that the DMSO concentration in the assay was < 0.2%. To evaluate the non-enzymatic degradation under assay conditions, a sample of each test compound was incubated also in the absence of hepatocytes. Samples were taken immediately and after 4 hours of incubation with test compounds. The incubation was stopped by adding the same volume of acetonitrile, vortexing and, freezing the reaction mixture. After thawing, vortexing, and centrifugation, the centrifugate was diluted with acidified (1% formic acid) water and analyzed for parent compound disappearance or metabolite appearance using LC/MS. The metabolic stability value corresponds to the remaining parent compound in % after 4 hours of incubation.

Results for BC-9842 in comparison to Example 154 from WO 2015/110481 A1 (12-epi-12- desvinyl-14-0-[(azepan-4-ylsulfanyl)-acetyl]-12-((E)-2-pyrid in-3-yl-ethenyl) mutilin hydrochloride) are summarized below.

BC-9842 displays a metabolic stability of > 60% after incubation with primary mouse hepatocytes and > 20% after incubation with primary human hepatocytes. Especially in comparison to the low metabolic stability of Example 154 from WO 2015/110481, this represents a valid improvement towards its usability as drug substance.