Tezacaftor VX-661  

Tezacaftor + Ivacaftor (SYMDEKO)

Tezacaftor + Ivacaftor + VX-659       

Tezacaftor + Ivacaftor + VX-445  

2018 Donaldson SH, Pilewski JM, Griese M, Cooke J, Viswanathan L, Tullis E, Davies JappearingC, Lekstrom-Himes JA, Wang LT; VX11-661-101 Study Group. Tezacaftor/Ivacaftor in Subjects with Cystic Fibrosis and F508del/F508del-CFTR or F508del/G551D-CFTR. Am J Respir Crit Care Med. 2018 Jan 15;197(2):214-224 [Pubmed]  Free PMC article

Scott H Donaldson

Tezacaftor (formerly VX-661) is an investigational small molecule that improves processing and trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) in vitro, and improves CFTR function alone and in combination with ivacaftor.   This is a study to evaluate safety and efficacy of tezacaftor monotherapy and tezacaftor/ivacaftor combination therapy in subjects with CF homozygous for F508del or compound heterozygous for F508del and G551D. This was a randomized, placebo-controlled, double-blind, multicenter, phase 2 study (NCT01531673). Subjects homozygous for F508del received tezacaftor (10 mg to 150 mg) qday alone or in combination with ivacaftor 150 mg q12h in a dose escalation phase, as well as in a dosage regimen-testing phase. Subjects compound heterozygous for F508del and G551D taking physician prescribed ivacaftor received tezacaftor 100 mg qday.

Primary endpoints were safety through day 56 and change in sweat chloride from baseline through day 28. Secondary endpoints included change in percent predicted FEV1 (ppFEV1) from baseline through day 28 and pharmacokinetics. The incidence of adverse events was similar across treatment arms.

Tezacaftor 100 mg qday/ivacaftor 150 mg q12h resulted in a 6.04 mmol/L decrease in sweat chloride and 3.75 percentage point increase in ppFEV¬1 in subjects homozygous for F508del and a 7.02 mmol/L decrease in sweat chloride and 4.60 percentage point increase in ppFEV¬1 in subjects compound heterozygous for F508del and G551D from baseline through day 28 (P < 0.05 for all).

The authors consider these results support continued clinical development of tezacaftor 100 mg qday in combination with ivacaftor 150 mg q12h in subjects with CF.

Dr. Scott H Donaldson (figure) is Associate Professor of Medicine, Pulmonary Diseases and Critical Care Medicine, University of North Carolina School of Medicine. 

Taylor-Cousar JLMunck AMcKone EFvan der Ent CKMoeller ASimard CWang LTIngenito EPMcKee CLu YLekstrom-Himes JElborn JS.  Tezacaftor-Ivacaftor in Patients with Cystic Fibrosis Homozygous for Phe508del. N Engl J Med. 2017 Nov 23;377(21):2013-2023. doi: 10.1056/NEJMoa1709846. Epub 2017 Nov 3. [Pubmed]

Jennifer Taylor-Cousar

In this phase 3, randomized, double-blind, multicenter, placebo-controlled, parallel-group trial, (NCT02347657) the authors evaluated combination therapy with tezacaftor and ivacaftor in patients 12 years of age or older who had cystic fibrosis and were homozygous for the CFTR Phe508del mutation. Patients were randomly assigned in a 1:1 ratio to receive either 100 mg of tezacaftor once daily and 150 mg of ivacaftor twice daily or matched placebo for 24 weeks. The primary end point was the absolute change in the percentage of the predicted forced expiratory volume in 1 second (FEV1) through week 24 (calculated in percentage points); relative change in the percentage of the predicted FEV1 through week 24 (calculated as a percentage) was a key secondary end point.

Of the 510 patients who underwent randomization, 509 received tezacaftor-ivacaftor or placebo, and 475 completed 24 weeks of the trial regimen. The mean FEV1 at baseline was 60.0% of the predicted value. The effects on the absolute and relative changes in the percentage of the predicted FEV1 in favour of tezacaftor-ivacaftor over placebo were 4.0 percentage points and 6.8%, respectively (P<0.001 for both comparisons). The rate of pulmonary exacerbation was 35% lower in the tezacaftor-ivacaftor group than in the placebo group (P=0.005). The incidence of adverse events was similar in the two groups. Most adverse events were of mild severity (in 41.8% of patients overall) or moderate severity (in 40.9% overall), and serious adverse events were less frequent with tezacaftor-ivacaftor (12.4%) than with placebo (18.2%). A total of 2.9% of patients discontinued the assigned regimen owing to adverse events. Fewer patients in the tezacaftor-ivacaftor group than in the placebo group had respiratory adverse events, none of which led to discontinuation.

The authors concluded the combination of tezacaftor and ivacaftor was efficacious and safe in patients 12 years of age or older who had cystic fibrosis and who were homozygous for the CFTR Phe508del mutation.

Dr Jennifer Taylor-Cousar (figure) is a paediatrician and adult pulmonologist in Denver, Colorado.

Kirby T.  Tezacaftor-ivacaftor is safe and efficacious in patients with cystic fibrosis with Phe508del mutations.  Lancet Respir Med. 2018 Jan;6(1):13-14. doi: 10.1016/S2213-2600(17)30439-3. Epub 2017 Dec 14. [Pubmed]    Two phase 3 double blind, randomised, placebo-controlled trials published in the  New England Journal of Medicine  show that treatment with the combination of tezacaftor-ivacaftor in patients with cystic fibrosis aged 12 years and older who have the common cystic fibrosis transmembrane conductance regulator (  CFTR  )     gene mutation, Phe508del, is both safe and efficacious.

–  This is a useful brief update by a medical journalist on the present trials and position regarding the recent tezacaftor-ivacaftor combinations with mention of encouraging developments in the triple combination therapy.

–  For details of the trial in Phe508del heterozygotes see Rowe et al. N Eng J Med 2017; 377:2024-35 ([Pubmed]); for that in Phe508del homozygotes see Taylor-Cousar et al. N Eng J Med 2017; 377:2013-23 ([Pubmed] both abstracted in the 2017 section of this History.

2018 Sala MAJain M. Tezacaftor for the treatment of cystic fibrosis.  Expert Rev Respir Med. 2018 Sep;12(9):725-732. doi: 10.1080/17476348.2018.1507741. Epub  2018 Aug 9.   [Pubmed]
 The newest modulator, tezacaftor, is a CFTR corrector that was recently approved by the FDA to be used in combination with the first approved CFTR potentiator, ivacaftor. Areas covered in this article include a  detailed review of the clinical trials and published literature, focusing on safety and efficacy, leading to the approval of tezacaftor in CF. Expert commentary: Recent trials have demonstrated that the combination of tezacaftor-ivacaftor is a slightly superior combination to its predecessor, lumacaftor-ivacaftor, with respect to an increase in FEV1, adverse event profile, and drug-drug interactions. It is also approved for a large number of non-F508del, residual function mutations that are predicted to respond based on in vitro testing. The horizon for continued improvements in CFTR-targeted treatments is promising, with three-drug combinations currently in Phase 3 clinical trials, and other drugs with novel mechanisms of action being studied. Within the next 5 years, the vast majority of patients with CF are expected to have a modulator approved for their genotype.

2018 Davies JCMoskowitz SMBrown CHorsley AMall MAMcKone EFPlant BJPrais DRamsey BWTaylor-Cousar JLTullis EUluer AMcKee CMRobertson SShilling RASimard CVan Goor FWaltz DXuan FYoung TRowe SMVX16-659-101 Study Group.VX-659-Tezacaftor-Ivacaftor in Patients with Cystic Fibrosis and One or Two Phe508del Alleles.N Engl J Med. 2018 Oct 25;379(17):1599-1611. doi: 10.1056/NEJMoa1807119. Epub  2018 Oct 18.  [Pubmed]

                 Jane Davies

The next-generation cystic fibrosis transmembrane conductance regulator (CFTR) corrector VX-659, in triple combination with tezacaftor and ivacaftor (VX-659-tezacaftor-ivacaftor), was developed to restore the function of Phe508del CFTR protein in patients with cystic fibrosis.         The effects of VX-659-tezacaftor-ivacaftor on the processing, trafficking, and function of Phe508del CFTR protein were investigated using human bronchial epithelial cells. A range of oral VX-659-tezacaftor-ivacaftor doses in triple combination were then evaluated in randomized, controlled, double-blind, multicenter trials involving patients with cystic fibrosis who were heterozygous for the Phe508del CFTR mutation and a minimal-function CFTR mutation (Phe508del-MF genotypes) or homozygous for the Phe508del CFTR mutation (Phe508del-Phe508del genotype). The primary end points were safety and the absolute change from baseline in the percentage of predicted forced expiratory volume in 1 second (FEV1).

RESULTS:(Trial numbers NCT03224351 and NCT03029455)                   VX-659-tezacaftor-ivacaftor significantly improved the processing and trafficking of Phe508del CFTR protein as well as chloride transport in vitro. In patients, VX-659-tezacaftor-ivacaftor had an acceptable safety and side-effect profile. Most adverse events were mild or moderate. VX-659-tezacaftor-ivacaftor resulted in significant mean increases in the percentage of predicted FEV1 through day 29 (P<0.001) of up to 13.3 points in patients with Phe508del-MF genotypes; in patients with the Phe508del-Phe508del genotype already receiving tezacaftor-ivacaftor, adding VX-659 resulted in a further 9.7-point increase in the percentage of predicted FEV1. The sweat chloride concentrations and scores on the respiratory domain of the Cystic Fibrosis Questionnaire-Revised improved in both patient populations.

The authors concluded robust in vitro activity of VX-659-tezacaftor-ivacaftor targeting Phe508del CFTR protein translated into improvements for patients with Phe508del-MF or Phe508del-Phe508del genotypes. VX-659 triple-combination regimens have the potential to treat the underlying cause of disease in approximately 90% of patients with cystic fibrosis.

2018 Carlile GWYang QMatthes ELiao JRadinovic SMiyamoto CRobert RHanrahan JWThomas DY.  A novel triple combination of pharmacological chaperones improves F508del-CFTR correction..  Sci Rep. 2018 Jul 30;8(1):11404. doi: 10.1038/s41598-018-29276-y.  Free PMC Article [Pubmed]

Pharmacological chaperones (e.g. VX-809, lumacaftor) that bind directly to F508del-CFTR and correct its mislocalization are promising therapeutics for Cystic Fibrosis (CF). However to date, individual correctors provide only ~4% improvement in lung function measured as FEV1, suggesting that multiple drugs will be needed to achieve substantial clinical benefit.

Here the authors examine if multiple sites for pharmacological chaperones exist and can be targeted to enhance the rescue of F508del-CFTR with the premise that additive or synergistic rescue by multiple pharmacological chaperones compared to single correctors indicates that they have different sites of action.                                                                                                                               First, they found that a combination of the pharmacological chaperones VX-809 and RDR1 provide additive correction of F508del-CFTR. Then using cellular thermal stability assays (CETSA) they demonstrated the possibility of a third pharmacologically important site using the novel pharmacological chaperone tool compound 4-methyl-N-[3-(morpholin-4-yl) quinoxalin-2-yl] benzenesulfonamide (MCG1516A). All three pharmacological chaperones appear to interact with the first nucleotide-binding domain (NBD1).

The triple combination of MCG1516A, RDR1, and VX-809 restored CFTR function to >20% that of non-CF cells in well differentiated HBE cells and to much higher levels in other cell types.                                                                      Thus they concluded the results suggest the presence of at least three distinct sites for pharmacological chaperones on F508del-CFTR NBD1, encouraging the development of triple corrector combinations.

2018 Keating DMarigowda GBurr LDaines CMall MAMcKone EFRamsey BWRowe SMSass LATullis EMcKee CMMoskowitz SMRobertson SSavage JSimard CVan Goor FWaltz DXuan FYoung TTaylor-Cousar JLVX16-445-001 Study Group.  VX-445-Tezacaftor-Ivacaftor in Patients with Cystic Fibrosis and One or Two Phe508del Alleles  N Engl J Med. 2018 Oct 25;379(17):1612-1620. doi: 10.1056/NEJMoa1807120. Epub  2018 Oct 18. [Pubmed

        Dominic Keating

VX-445 is a next-generation cystic fibrosis transmembrane conductance regulator (CFTR) corrector designed to restore Phe508del CFTR protein function in patients with cystic fibrosis when administered with tezacaftor and ivacaftor (VX-445-tezacaftor-ivacaftor).                                                     The authors evaluated the effects of VX-445-tezacaftor-ivacaftor on Phe508del CFTR protein processing, trafficking, and chloride transport in human bronchial epithelial cells. On the basis of in vitro activity, a randomized, placebo-controlled, double-blind, dose-ranging, phase 2 trial was conducted to evaluate oral VX-445-tezacaftor-ivacaftor in patients heterozygous for the Phe508del CFTR mutation and a minimal-function mutation (Phe508del-MF) and in patients homozygous for the Phe508del CFTR mutation (Phe508del-Phe508del) after tezacaftor-ivacaftor run-in. Primary end points were safety and absolute change in percentage of predicted forced expiratory volume in 1 second (FEV1) from baseline.

Results. In vitro, VX-445-tezacaftor-ivacaftor significantly improved Phe508del CFTR protein processing, trafficking, and chloride transport to a greater extent than any two of these agents in dual combination.   In patients with cystic fibrosis, VX-445-tezacaftor-ivacaftor had an acceptable safety and side-effect profile. Most adverse events were mild or moderate. The treatment also resulted in an increased percentage of predicted FEV1 of up to 13.8 points in the Phe508del-MF group (P<0.001). In patients in the Phe508del-Phe508del group, who were already receiving tezacaftor-ivacaftor, the addition of VX-445 resulted in an 11.0-point increase in the percentage of predicted FEV1 (P<0.001). In both groups, there was a decrease in sweat chloride concentrations and improvement in the respiratory domain score on the Cystic Fibrosis Questionnaire-Revised.

The authors concluded the use of VX-445-tezacaftor-ivacaftor to target Phe508del CFTR protein resulted in increased CFTR function in vitro and translated to improvements in patients with cystic fibrosis with one or two Phe508del alleles. This approach has the potential to treat the underlying cause of cystic fibrosis in approximately 90% of patients.     (Clinical trials NCT03227471 ; and EudraCT number, 2017-000797-11)

Dominic T Keating is Respiratory Physician at the Alfred Hospital · Department of Allergy, Immunology & Respiratory Medicine (AIRmed)  Australia, Melbourne