CRISPR Therapeutics Provides First ANGPTL3 Data

Good morning, biotech.

Yesterday, regulatory uncertainty hit fever pitch with the appointment of Dr. Vinay Prasad to head the CBER division regulating biologics, including gene therapies and genome editing at the FDA.  Instead of assuming the worst for this line of drug development, I remain a firm believer that those that matter most, very sick people, will continue to push for medicines that can be shown to be safe and effective, and that Dr Prasad keeps to his view that the FDA should not make it harder, and therefore more costly, to develop drugs for severe rare diseases which have shown promise.

With that out of the way, let’s dive into the first data snapshot provided by CRISPR Therapeutics on its first-in-human trial with CTX310 (Cas9 knockout of ANGPTL3) for disorders related to high lipds, especially triglycerides and LDL cholesterol.

 

ANGPTL3 as a genetically and pharmacologically validated target

There is strong genetic evidence that reduced ANGPTL3 activity is associated with cardiovascular benefit.  A (life-long) 50% reduction in ANGPTL3 due to heterozygous loss-of-function variants cuts the odds of developing cardiac artery disease by almost half (Dewey et al,2017).  These subjects have modestly lower triglyceride (-27%) and LDL-cholesterol (-9%) levels.

Pharmacologic inhibition is even more impactful.  The ANGPTL3-targeting monoclonal antibody evinacumab from Regeneron for example lowers TG by about -80% in hypertriglyeridemia patients (Ahmad et al, 2019).  RNAi knockdown with ARO-ANGPTL3 from Arrowhead Pharmaceuticals with an ANGPTL3 knockdown efficiency of ~-70% resulted in approximately -60% TG, -60% remnant cholesterol (known ASCVD risk factor), and a modest -10% LDL-cholesterol reduction in mixed hyperlipidemia patients (Rosenson et al, 2024).

It should be noted, however, that besides an approval in very rare homozygous familial hypercholesterolemia, approval and development in other indications has somewhat stalled with ANGPTL3 inhibitors/knockdown agents.  Indeed, a study with evinacumab in multifactorial severe hypertriglyceridemia subjects failed to show statistically significant triglyceride lowering (Rosenson et al 2023)!  This and the fact that outcomes studies using non-genome editing modalities are lacking, makes ANGPTL3 potentially the most difficult cardiovascular disease target to bring to a large patient populations among the PCSK9, Lpa, and ANGPTL3 trifecta.

 

CTX310 shows steep dose response…and a surprise

CTX310 is an LNP formulation comprising an mRNA encoding Cas9 nuclease and a guide RNA aimed at the angiopoietin-like 3 gene.  Although the company wants to develop CTX310 for homozygous familial hypercholesterolemia which is characterized by LDL-receptor deficiency, the same receptor that standard LNPs rely on for uptake in hepatocyte, I assume that CTX310 does not include ASGPR-targeting via the addition of GalNAc ligands.

CTX310 was tested at 4 doses. It should be added here that the company provided doses on the ‘basis of lean body weight’ probably in the hope that it may in fact be a better predictor of drug delivery to the liver compared to dosing based on pure body weight or fixed doses.

Anyway, the 2 lowest doses (0.1 and 0.3mg/kg) showed no desired pharmacodynamic effect.  In fact, mean LDL-cholesterol strangely increased from baseline by 35% just 30 days after drug administration (n=3).  At 0.6mg/kg (n=3) and 0.8mg/kg (n=1; ~0.48mg/kg not adjusted for lean muscle), however, there was knockdown of serum ANGPTL3 of ‘up to -75%’ with concomitant decreases of TGs and LDLc of -56% and - 29%, respectively, at 0.6mg/kg.  At 0.8mg/kg the company reported a remarkable -65% LDL-cholesterol reduction on day 30 reaching a whopping -80% on day 90 in a patient with severe hypertriglyceridemia (TG>500mg/dL).  Triglycerides were also lowered by over -80% in this subject.

Safety findings, particular in terms of changes in liver enzymes and platelets, were characterized as 'not clinically significant', and clearly need further disclosure.  

Also because of its likely non-ASGPR-targeting nature, severe hypertriglyceridemia should be the most promising indication for CTX310, for example to prevent pancreatitis. The LDL cholesterol effects, however, warrant further investigation and may justify development for ASCVD.  Given that this was seen in just one subject, the 0.1 and 0.3mg/kg LDL-cholesterol increases in LDLc indicating there may be something odd with the assay, and that it is in great contrast to the genetic and pharmacodynamic evidence presented above, further subjects dosed at 0.8mg/kg may not show such dramatic effects.  If the values are real, however, and given the near opposite findings with evinacumab in severe hypertriglyceridemia, a closer look at the genetics of this subject may lead to fresh insights into lipid biology and render ANGPTL3 a more predictable target.

RNAi is the Future of Cardiovascular Disease

At least, this is what Big Pharma and Biotech is saying right now following deals between pure-play RNAi companies Arrowhead Pharmaceuticals and Dicerna with Amgen and Eli Lilly, respectively, and the sale of The Medicines Company with its lead PCSK9 RNAi asset really being only a matter of timing.  Besides its new relationship with Eli Lilly announced yesterday, Dicerna has an ongoin CVD-related NASH/NAFLD collaboration with Boehringer-Ingelheim.  In addition, Wave Life Sciences and Akcea, the commercial Ionis spin-out, have been pursuing cardiovascular targets along with Pfizer and Novartis, respectively, using the competitive RNaseH antisense gene knockdown technology.

Drugging the undruggable

Part of the attraction of RNAi for CVD for the pharmaceutical industry is because the targets that come from large genetic studies (e.g. ApoCIII, Apo(a), ANGPTL3) based on chance alone are not readily druggable.  To make matters worse, amorphous lipid macromolecular aggregates are particularly difficult to target with either small molecules or antibodies.

Infrequent dosing

What a difference 10 years can make.  When Protiva (now Arbutus) was one of the first to enter a systemically administered RNAi therapeutic against LDLc-related ApoB into the clinic a decade ago, it often found itself ridiculed for using RNAi in such an indication.  Systemic RNAi back then required relatively frequent (1-3 weeks) intravenous administration which would make it an unlikely modality for widespread diseases that ideally require decade-long preventive treatment strategies.

Fast-forward to the present and now we have subcutaneously delivered RNAi with potential dosing frequencies of up to once-a-year as evidenced by the lead candidate of this crop, phase III asset Inclisiran by The Medicines Company.  If the remarkable safety profile holds up following about 2000 patient years of clinical experience, such a drug should be very widely prescribed, not least because it should enjoy great adherence, one of the major impediments of treatment success in cardiovascular disease.   

Undoubtedly, it has been the Inclisiran performance so far that has attracted the attention of players like Eli Lilly and Amgen, the latter of which, of course, should know particularly well about the competitive threat from RNAi having an antibody-based PCSK9 agent on the market (Repatha).  Beyond the upcoming slew of phase III read-outs with Inclisiran, it will equally be interesting to see the types of new targets being pursued and the clinical validation of targets like Apo(a) by the antisense competition.

Busy Week in Oligonucleotide Therapeutics

Ionis-Akcea ApoCIII Panel

Alnylam CNS Aspirations

Arrowhead Cardiovascular Data 

Dicerna Deal Pre-Announcement

It’s been a very busy week in the Oligonucleotide Therapeutics space, so I thought to memorialize the most important events of last week with this blog entry. 

Difficult Volanesorsen Panel

The highlight of the week certainly was the Advisory Committee on Volanesorsen (VLN; commercial name WAYLIVRA) for the treatment of Familial Chylomicronemia Syndrome (FCS) hypertriglyceridemia.  Here, the FDA, experts in the field, and sponsor Akcea Therapeutics were struggling to assess the risk:benefit of the ApoCIII-targeting phosphorothioate antisense gapmer. I had previewed the panel here.  

As I had expected, the majority voted yes on whether VLN should be approved for FCS.  

While following a very strict diet can be a powerful risk mitigator in FCS, it greatly affects quality of life and alone cannot absolve patients from the risk of pancreatitis attacks, abdominal pain and a range of other morbidities related to having very high triglyceride levels in the blood.  Because VLN is by far the most effective agent for lowering triglyceride, I would have been very surprised in this era of patient choice if a panel of experts wanted it to be out of reach for them.

Unfortunately, aside from on-target pharmacological efficacy, VLN performed very poor in terms of safety and tolerability.  Moreover, the trial was too small and ill-designed to tease out real disease benefits such as a lower pancreatitis attack rate and improved quality of life.  Not even a trend in favor of VLN could be discerned here.

As a result, the discussion was mostly centered around what an effective risk mitigation program (REMS) could look like to prevent dangerous bleeding events caused by the thrombocyte-(= platelet-) suppressing activity of VLN, the adverse event that was singled out as most concerning. 

Unfortunately, the practical experience with VLN showed that even closely following platelet counts and stopping VLN administration or adjusting dosing frequency in response to dropping levels are not able to stop such bleeding risk from continuing.  As such, it is to be expected that VLN will get onto the market without a really satisfactory REMS and that patients may have to accept the bleeding risk, knowing that treating physicians will be ready to administer steroids and/or IVIG should platelets drop to extremely low levels.

Due to thrombocytopenia and the range of other safety and tolerability issues and safety monitoring demands, there is a real possibility that VLN will mostly be a placeholder until safer ApoCIII-lowering alternatives can get approved.  In light of what we have learned from mipomersen and TTR-lowering drug Inotersen, the most negative impact of the VLN data is probably on the potential of systemically administered phosphorothioate antisense oligos outside of the liver.  While GalNAc for the liver and potentially GLP-1 peptides for pancreatic beta cells should keep required ASO levels substantially below the 200-300mg/week dose known to cause the tox and tolerability issues, the prospect for tissues, including muscle, that require systemic ASO administrations is less bright.

Having said that, there could be very simple solutions such as minimal reductions in the extent of phosphorothioation that miraculously can get rid of most of these side effects.  In the absence of a reliable animal model system, however, learning the rules in the clinic could take quite a few more years.  

Alnylam announces CNS aspirations

Another highlight of the week in Oligonucleotide Therapeutics was Alnylam’scoming out in applying RNAi for gene knockdown in the central nervous system (see presentation here). 

While CNS had been an area of interest of the company in its early days (Huntington’s Disease collaboration with Medtronic, a Parkinson’s program), the direct intrastriatal injection results and delivery approaches with old RNAi trigger formats were far from promising for clinical translation.  Not surprisingly, CNS had dropped off the corporate radar.

With the lesson learned from GalNAc-RNAi for the liver, most notably that of the importance of high chemical stabilization and ligands to maximize both oligonucleotide concentration and cellular uptake, and the surprisingly broad CNS biodistribution seen following intrathecal administration of antisense oligonucleotides by Ionis, it was only a matter of time that companies in the RNAi space would re-visit ‘old tissues’ for RNAi.  So with Arrowhead stoking interest in its RNAi efforts in the lung and Alnylam now in the CNS, RNAi is on the cusp of shedding its perception that it is ‘only for the liver’.  And unlike Ionis and Akcea, the RNAi space has street cred so that the capital markets are likely to buy into those claims.

To make matters worse for Ionis, Alnylam is now predicting that (similar to the liver), knockdown with its RNAi molecules should be longer-lived and much better tolerated than the phosphorotioate competition (from Ionis and Biogen): 

'Expect superior potency, duration and systemic safety profile vs. ASOs'

In light of the limited though promising public data (single rat intrathecal injection of 0.9mg of RNAi trigger causing substantial, ~75% target gene lowering for at least 1 month, the latest time point measured), it is too early to decide whether that’s true.  More information on this subject should, however, emerge over the next 2 years by which time Alnylam plans to file its first IND for the CNS.

Arrowhead highlights cardiovascular pipeline

Arrowhead Pharmaceuticals seems to have repaired relationships with investors following its DPC Waterloo and is increasingly getting credit for its GalNAc-based turnaround.  Outside of its lead programs in HBV and AAT-related liver disease, it is cardiovascular disease indications that are the focus of these efforts.

So at ATVB, the company presented an update on these programs with a focus on ANGPTL3 for the treatment of a range of lipid-related abnormalities, especially hypertriglyceridemia.  Of note, first monkey data showed that the administration of therapeutically relevant 3mg/kg triggered robust, 80% target gene knockdown lasting for more than 4 weeks. 

With INDs/CTAs planned for both ANGPTL3 and ApoCIII as well as potentially Lp(a) by partner Amgen anticipated before the end of the year, 2019 promises to be a clinical data-rich year for RNAi in cardiovascular disease.

Dicerna kind of pre-announces AAT-deal as investors get ready to sell shares

Much of what is going on behind the scenes at Dicerna is currently only being reflected by its SEC filings.  

On May 4, large shareholders who had supported the company throughout its litigation with Alnylam and now stand to be richly rewarded for it (~5x gain currently) had their shares registered for sale in an S-3 filing.  These shares account for a whopping roughly half of the shares outstanding.

To bring all investors up to speed, such a registration necessitates the filing of a prospectus.  Interestingly, this document was very specific in that the company now expects to partner the mystery orphan-disease candidate it has been talking about for quite some time this quarter:

‘We plan to seek a risk-sharing collaborator for this program before we file an IND and/or CTA, which we expect to be prepared to file in the second quarter of 2018.’

The document also removes any doubt that the secret target of that program is alpha-1-antitrypsin:

‘The protein causes progressive liver damage and fibrosis, in some cases leading to cirrhosis and liver failure, and we believe that silencing of the disease gene will prevent production of the abnormal protein and thereby slow or stop progression of the liver fibrosis. Greater than 100,000 people in the United States (“U.S.”) are believed to be homozygous (i.e. having identical pairs of genes for any given pair of hereditary characteristics) for the mutation that causes the liver disease, and at least 20% of those people, and potentially a significantly higher fraction, are believed to have liver-associated disease as a consequence.’

So if you were mesmerized by the stocks recent strong performance on modest volume, here’s a conspiracy theory: the company is helping supportive investors to get out on a high volume day that an AAT deal announcement would precipitate.  And spending a few bucks to run the shares up is well worth the investment. 

If the events unfolds as I speculate, it is yet another powerful reminder it is not sufficient for investors to merely follow the press releases, but carefully read the regulatory filings, even if they may seem dry and overly long. 

Addendum 15May18: on its quarterly conference call, Dicerna clarified its convoluted statement in the prospectus regarding the timing of partnership and IND of the mystery candidate. Accordingly, the candidate will be ready for IND/CTA filing by the end of Q2. An actual filing, however, will have to await a partnership which the company now guides for the second half of this year.  Apparently, they are currently in talks with 'more than two' potential partners.

Another focal point of the conference call Q&A session was the rationale behind the single-dose trial with DCR-PHXC for primary hyperoxaluria and how they want to use that as the basis for designing a pivotal registrational, multi-dose trial in 2019.  In this regard, contradictory statements were made.  On the one hand, the CMO contended that as seen with the more advanced program by Alnylam, most of the oxalate lowering can be seen following a single dose already so the company will have a good idea as to the necessary dose and dosing frequency for the pivotal trial.  On the other hand, the CEO predicted that repeat dosing is likely to be necessary to get an idea as to the actual oxalate-lowering potential of a given dose.  Here, I side with the CEO, but keep asking myself why on earth are they taking so much scientific and regulatory risk with a single-dose trial?