Patogeneze virových nákaz Antivirová terapie Patogeneze virových nákaz

Cíle antivirových látek POSSIBLE PHASES OF LIFE CYCLE ON WHICH ANTI-VIRAL ATTACK MIGHT BE LAUNCHED 1) Attachment to cell surface, perhaps competition with a specific viral receptor 2) Uptake into intracellular vesicles (endosomes) 3) Uncoating of virus (loss of protein coat, fusion of lipid membrane with endosome/lysosome). Note: the endosome/lysosome compartment is acidic and inhibition of acidification of this compartment might be a good target 4) Replication of genome to new RNA or DNA (polymerases are the target) 5) mRNA transcription 6) mRNA processing (poly A, methylation, capping, splicing) 7) Translation to protein 8) Post-translational modification of proteins (glycosylation, phosphorylation, fatty acylation, proteolysis). Some of these are essential for functional, infective viral progeny. 9) Assembly of the components into the whole virus

ADSORPTION to cell membrane Sites of attack of approved antivirals Sites of attack of developmental antivirals CELL POOL (AMINO ACIDS, SUGARS, ...) FUSION, ENTRY to cell VIRAL PROTEINS SYNTHESIS OF VIRAL PROTEINS de novo VIRION DISSOCIATION INFECTIVE NA (DNA, RNA) TRANSCRIPTION de novo TO VIRAL NK MATURATION OF VIRAL PROTEINS de novo VIRAL NA REPLICATION MATURATION OF VIRAL NA de novo VIRUS ASSEMBLY CELL POOL (NUCLEOTIDES, SUGARS, ...) VIRUS BUDDING INTEGRATION INTO NUCLEAR DNA (RETROVIRUSES)

TRPĚLIVOST ! Vývoj antivirotika trvá přibližně 15 let 6.5 years 1.5 years 2 years 3.5 years 1.5 years Discovery and preclinical testing Phase I Phase II Phase III FDA review Phase IV (postmarketing testing) Clinical trials WHAT WILL BE NEEDED IN 15 YEARS ?

Klinické hodnocení léčiv probíhá ve třech fázích: Fáze 1 je prováděna na 20-80 zdravých dobrovolnících a trvá přibližně 6-9 měsíců. Cílem fáze 1 je zjištění rozdílné toxicity u lidí v porovnání s pokusnými zvířaty. Determinuje se závislost počtu vedlejších účinků na zvolené dávce. Fáze 2 se provádí na 100-500 pacientech trpících chorobou, pro kterou je léčivo indikováno a trvá většinou 6 měsíců až 3 roky. Cílem této fáze je ověření účinnosti léčiva a jeho bezpečnosti. Jedna skupina pacientů dostává léčivo a druhá placebo, obvykle jsou tyto studie randomizované (pacienti dostávají léčivo nebo placebo na základě náhodného výběru). Většina těchto studií je také dvojitě zaslepená („double-blinded“) s tím, že ani lékař ani pacient neví, jestli dostávají léčivo nebo placebo. Fáze 3 se účastní 1000-5000 pacientů trpících chorobou, pro kterou je léčivo indikováno a je většinou nejdelší (1-4 roky). Jedná se o podrobnou studii účinnosti a bezpečnosti experimentálního léčiva. Většinou se jedná o dvojitě zaslepené randomizované studie.

1 year validity 15 years DISCOVERY In countries where the patent was not granted or applied for, it is not necessary to respect it. However, noone else will be allowed to file similar application. DISCOVERY very expensive !!! secrecy 1 year Primary patent application filing International patent application patent examination by the patent offices in individual countries new compound LICENSE > new method Drug development > novel use DRUG GENERICS Patent granting validity 15 years Patent is worthless if it is not realized directly or licensed.

NEW DRUG DEVELOPMENT - CLINICAL PHASE FIRST APPLICATION TO HEALTHY VOLUNTEER REGISTRATION & APPROVAL OF CLINICAL STUDIES (I.N.D.) NEW DRUG DEVELOPMENT - CLINICAL PHASE INCREASED DOSAGE ESTIMATION OF SAFE DOSAGE FIRST APPLICATION TO PATIENT ESTIMATION OF EFFICACY AT SAFE DOSIS COMPARING WITH AN APPROVED DRUG CHARAKTERISATION OF SIDE EFFECTS PLACEBO STUDY SIDE EFFECTS, CONTRAINDICATION PLACEBO STUDY AT AN INCREASED DOSAGE APPROVAL PROCESS FOR LIMITED USE DOUBLE PLACEBO STUDY

Nucleoside antivirals and cytostatics interfere with the replication of viral and cellular nucleic acids. Their targets are: DNA polymerases for DNA viruses (replication of viral DNA) RNA-dependent RNA polymerases for RNA viruses (catalyze replication of viral RNA) reverse transcriptases for retroviruses e.g. HIV (transcription of retroviral RNA to proviral DNA) or telomerase. nucleoside kinase NMP kinase NDP kinase Nuc-OH Nuc-p Nuc-pp Nuc-ppp To become active, nucleosides must be converted by stepwise transformation to their mono-, di- and triphosphates. The efficacy of the first step may be in some cells limited. In those cases, the efficacy of the nucleoside antimetabolite therapy sometimes fails. Our acyclic nucleoside phosphonates (ANP’s) largely circumvent this obstacle - they are analogues of nucleoside monophosphates.

Single pill contains daily dose of two types of reverse transcriptase inhibitors: nucleoside analogue emtricitabine (Coviracil™) and ANP prodrug tenofovir disoproxil fumarate (Viread™). This new AIDS drug Truvada™ was approved in the U.S.A. in 2004 and the approval by EMEA is pending. An agreement has been signed to develop a triple combination with non-nucleoside reverse transcriptase inhibitor efavirenz (Sustiva™). Why combinations? In AIDS therapy the patients take five to six drugs several times a day. The dosage and application regimen must be strictly observed. It is difficult to warrant, particularly in the countries with the highest AIDS occurence. Ideally, there should be a single pill containing total daily doses of all drugs in question. It is so far impossible, due to the drug interactions, frequent need for alteration of drugs inside the individual groups and diverse timing with regard to food intake.