David's New Book

Wednesday, August 24, 2016

Pfizer and Astrazeneca

What goes around comes around.

Today Astrazeneca and Pfizer announced that they had entered into an agreement where AZ would license their marketed antibiotics (Merem, Zinforo and Zavicefta) and those in development to Pfizer.  Pfizer will pay AZ $550 million upfront and $190 million in January (total $740 million). There are also a number of milestone payments envisioned that could bring the total cash payments close to $2 billion.  In addition, AZ will reap double-digit royalties on sales. Medimmune and Entasis were both excluded from the deal.

To put this deal in perspective, AZ paid $350 million upfront for Novexel and what is now Zavicefta (plus other assets none of which have yet made it to market). 

Back in 2013 Astrazeneca announced that it would focus on areas outside of infectious diseases. They stated that they wanted to “partner” their anti-infectives efforts going forward. Since then, the infectious diseases franchise at AZ has been up for sale to the highest bidder.  What’s been going on for the last three years? No one was bidding high enough for AZ (or at least that’s what I deduce based on my discussions with those trying to make a deal with AZ). There were apparently two problems.  First, we are talking about ex-North American rights. Second, AZ had a rather inflated idea of the value of their products (according to my contacts). During this time, AZ spun out their antibiotic discovery group to form Entasis. And they formed a fully-fledged business unit out of their antibiotic development group. 

In 2011, Pfizer abandoned antibiotic research entirely. They fired all (or almost all) of their anti-infectives researchers and developers.  They also downsized their entire research effort globally by almost 25%. This occurred in a company with a rich history in antibiotic discovery and development.  Pfizer was one of the first companies to join the antibiotic revolution with penicillin. Then came the first, good, oral tetracycline, doxycycline in the 1960s. Later came the beta-lactamase inhibitor, sulbactam. Diflucan or fluconazole was invented at Pfizer’s facility in Sandwich, UK in the 1990s. They acquired Zyvox through their purchase of Pharmacia. With their acquisition of Wyeth, they had piperacillin-tazobactam and tigecycline. How could a company with this history abandon antibiotics research in the way that it did?

What’s now left at Pfizer? Apparently there is still a small core of antibiotic developers there.   A few of the researchers involved in antibiotics moved over to Pfizer Vaccines (previously Wyeth Vaccines). Some moved to other therapeutic areas within Pfizer.  But the vast majority are long gone.  Many went to AZ and are now either working elsewhere or at Entasis or are unemployed. But – I understand that there will be a significant transition period where the AZ developers will be able to support Pfizer’s efforts and even provide experience and guidance going forward. They may even get a shot at a job in Pfizer. So this might work better than if, say, Pfizer were just to jump back in the way the Roche did.

On the one hand, I want to be excited that Pfizer is getting back into the antibiotics business. Companies that have lost their expertise in antibiotics can struggle for years to regain their footing. My contacts suggest that the transition from AZ to Pfizer is structured such that this will be a smooth process and will avoid this struggle. I take their word for it, but I’ll be watching.

In terms of big pharma companies still doing antibiotics R&D – the numbers haven’t changed.  We’ve just replaced AZ with Pfizer.  It’s a shell game.

I still find it depressing that those who worked so hard to bring exciting, new antibiotics like ceftazidime-avibactam to market at AZ, now, once again, face an uncertain future.

Thursday, August 11, 2016

Confounding Aminoglycosides?

I’m still stuck on the recent FDA meetings where pathways to regulatory approval for pathogen-specific antibiotics were discussed. The example chosen to illustrate the challenges in identifying a pathway was a fictional drug called X-1 that was entirely specific for Pseudomonas aeruginosa. I suggested a superiority design trial where patients with a high risk for Pseudomonas infection would be enrolled and treated with a combination of a carbapenem, X-1 and, if desired, an aminoglycoside. Controls would include those treated with only the carbapenem plus (or not) aminoglycoside. As I noted, the centers would have to be those where there was a rate of carbapenem-resistance among Pseudomonas but not at such a high level that physicians would feel uncomfortable with empiric carbapenem therapy.  (Globally, the rate for carbapenem resistance in this organism is in the range of 15-20% range.  In this range, most patients are still treated empirically with a carbapenem, usually in combination with an aminoglycoside).   In my design, I suggested that the evaluable population for analysis of superiority would, in fact, be those with carbapenem-resistant infections.

The response I received was a horrified, “But the aminoglycoside is an active drug.  It will confound your results.  You will never know what to attribute to X-1 vs. the aminoglycoside!” Some insisted this would be true even if the aminoglycoside were only administered for the first few days of therapy. I beg to differ (at least for serious infections outside the urinary tract).

There are a number of studies examining the effect of aminoglycosides on Pseudomonas aeruginosa infections. One, from Leibovici et. al. in Israel.  In their prospective observational study, they were unable to demonstrate an advantage of adding an aminoglycoside to B-lactam therapy outside of those patients who were neutropenic and those with bacteremia. But more interesting was that for patients where the aminoglycoside was the only “appropriate” drug based on susceptibility testing, patients had a 40-100% higher mortality compared to appropriate beta-lactam monotherapy.

Another study looked at bacteremia caused by Pseudomonas aeruginosa. In this study from Spain, it appeared as though a higher mortality among those treated “appropriately” was mostly due to those who received an aminoglycoside as the only active drug.

Several other studies confirm the lack of an advantage for combination therapy of beta-lactam plus aminoglycoside compared to beta-lactam alone in treating these infections. Several, like the two I noted here, suggest that there is a treatment disadvantage when, in fact, an aminoglycoside is the only active drug in the regimen.  These studies suggest to me that a few days of an aminoglycoside in the design I suggested would be anything but confounding.

Friday, July 29, 2016

Money for New Antibiotics - What Could be Wrong with That?

I was beaming with pride in those who worked to bring the public-private effort to fund a major new effort in the discovery and development of antibiotics as was announced yesterday. CARB-X will establish a sort of incubator for academic groups and small or even mid-size companies, potential spin-offs and others working on early to mid-stage antibiotic development. The entity is a partnership between Boston University Law School (I’ll try and explain below), the Department of Health and Human Services (BARDA) in the US, the Wellcome Trust in the UK and the new AMR Centre also in the UK.  The National Institutes of Health will provide “in kind” support like access to their preclinical services.

The really good thing about this is the clear recognition by people with money that we need to develop new antibiotics to address the emerging problems of antibiotic resistance today and those that will surely be here tomorrow. Another potentially important aspect of this is the coalition that brought this forward. But why Boston University Law School? Maybe because that is where Kevin Outterson is.  BU will be the center of the advisory board for the effort and will include a mix of scientists and clinical developers with experience in antibiotics. There will obviously be legal issues around the formation of new companies, patents, intellectual property and other topics that will require legal advice. Having a legal team available to help will be important going forward.

I consider this a very important step forward.  But at the same time, I have a few thoughts for us to consider (and I’m not the only one). According to Kim Lewis, who spoke with Asher Mullard for Nature (quoted here in Scientific American), “If more money is going into the general area of antibiotics, that’s a good thing. But I’m really surprised that we are getting another influx of funds into development rather than into discovery.” The main problem, says Lewis, is the lack of compounds that can punch through the outer membranes of ‘gram-negative’ super-microbes such as Escherichia coli and Klebsiella pneumoniae. Researchers need to work out how to systematically make or find compounds that can slip through bacterial protective barriers, he says. And Kim is right. As Kim points out, we need new compounds to develop.  We absolutely need more money for fundamental antibiotic discovery research.  The NIH has been woefully behind in their efforts in this important area (although they have just had a new influx of funds).  Their “in kind” support mechanisms are helpful, but extremely slow and bureaucratically cumbersome to use.  Sure – if you have no choice these services are a lifesaver for academics or even small companies. But this could be done much more efficiently.

The other problem I have been harping on (to no avail) for the last 12 years is the lack of training for our antibiotic researchers and developers.  Perhaps the CARB-X  will provide this training as well, but it seems to me that those who are untrained are simply not likely to be funded or “placed” in the incubator.

Erik Gordon, professor at the University of Michigan's Ross School of Business, speaking to CIDRAP News, was even more skeptical. "Antibiotic development needs the backing of non-profit organizations to make the economics work," he said. He added, however, "I'm not sure funneling that much money into an accelerator system based at a law school, where few antibiotics have ever been developed, with so many cooks, is the best use of the money or the best way to develop the new antibiotics we need."

Another looming problem to be addressed has nothing to do with money.  At least some, if not most, of the antibacterial compounds that will come out of CARB-X will be adjunctive therapies or perhaps pathogen-specific therapies.  We need a clear and feasible regulatory pathway for the development of these compounds.

And this brings me, finally, to post-market or “pull” incentives.  That’s where the rubber hits the road, folks.  Very simply, if we don’t make the economics work for antibiotics, we won’t have any.

Wednesday, July 20, 2016

FDA Workshop on Pathogen-Specific Antibiotics - Part 2

To continue our discussion of the FDA Workshop on the development of pathogen-specific antibiotics, I’ll start briefly with a discussion of statistical issues and approaches that concluded day 1 of the meeting.  Honestly, since it was a fairly authoritative and intense set of presentations that left me n the dust, I have little to say other than to refer you to the slides. What was clear is that there are a number of Bayesian methods that would allow for a more comprehensive analysis of trials where the numbers are small.  Enough said.

The second day of the workshop was the meat of the meeting and was set-up by our discussion on the first day.  John Rex and colleagues invented a fictional drug they called X-1 that was active only against Pseudomonas aeruginosa.  They then set about trying to design a non-inferiority trial to compare the new drug to a comparator agent – in this case, meropenem.  Why, I asked myself, did he start with a non-inferiority design. In trying to read John’s mind, I thought the following. (1) NI trials are the most reliable way to antibiotic approval and have been used for the approval of new agents (like ceftazidime-avibactam). (2) The exercise would expose in a very quantitative way the costs and risks of such a program. (3) The discussion would stimulate thinking about new approaches to the NI design or to thinking about other designs.  You can find all the details about X-1 in the slide packages provided for the meeting.

John started with a few assumptions and limitations.  The most important was that the trial could not exceed 1000 patients for cost and time reasons. Given the numbers of potentially enrollable patients with these infections, mostly HAP/VAP and IAI, under the usual circumstances of such a trial, you cannot meet the 1000 patient limitation. The proportion of Pseudomonas infections among enrolled patients is just too small. So, to meet this goal required several manipulations.  First, a wide NI margin of 30% is required for HAP/VAP and 25% for IAI.  He was able to justify this in that for HAP/VAP he used the FDA endpoint of 28 day all cause mortality in the microbiologically documented population and for IAI he used cure in the microbiologically documented population as endpoints based on the FDA’s own guidance documents.  The development of agents for patients with unmet needs specifically states that wider NI margins could be considered and the margins chosen lie within the crude M1 calculations provided by the FDA. The design involved the use of X-1 + ertapenem (erta is not active vs. Pseudomonas) vs. meropenem.  Investigators were allowed to add amikacin to each arm for up to 4 days initially (a potential confounder). Even with these wide NI margins, to reduce the trial size, John had to invent a rapid, bedside test for the diagnosis of Pseudomonas in respiratory secretions or abdominal culture swabs to increase the chances of culture-positivity. This led to a total of almost 1900 screened patients in the two indications and 915 enrolled. Then came the results.  Based on John’s impeccable math, 175 patients with Pseudomonas across the two indications were treated divided in a 2:1 randomization schedule. You can see that the numbers are going to be small.  The table shows numbers achieving the endpoint over the total treated for each treatment group and each indication. These fit within the prescribed margins. But what if one or two patients are moved or removed on various sides of this table?  It can all rapidly fall apart.  What if there is no diagnostic test or if the test used fails to predict culture positivity?  The numbers then become really small. In all cases, the conclusions based on the trial, whether positive or negative, are very fragile.

 I was convinced from the beginning, and even more so after all of John’s marvelous mathematical scenarios and contortions, that such a trial would be too risky, too expensive and would expose too many patients to an unknown drug that might well still be unknown at the end of the study.  I made the statement that no one would run such a trial.  Jeff Lowtit from the Medicines Company then promptly jumped up and said that he would run such a trial! Nevertheless, it was clear to all in the room what the costs and risks of such a trial would be and what the prospects for funding and for return on investment in such a scenario would be.  It was not a pretty picture. One caveat – could a Bayesian approach substantially de-risk the NI venture?

I suggested that we should abandon the NI trial design concept for such a drug altogether and go towards a superiority design approach as I have argued consistently in the past.  Even here, there are major problems. (1) External controls are probably required as well as some sort of within-trial validation set to show that control levels of response are real. (2) Even with such controls, the trial might not be inferential at the P=.05 level – although possibly it would be for P=.1 or .2.  The trial would probably have to include amikacin for several days in both arms thus failing to avoid this potential confounder.  This puts the trial at higher risk and the addition of amikacin would have to be factored in to the external controls one would use. As I have discussed, such control levels of response could be established pre-trial – so the calculations could be more informed.

Now imagine the situation where infections are even less frequent such as would be the case for Acinetobacter infections.

Paul Ambrose kept coming back to the same theme – and not without justification.  If the trials are not inferential, wouldn’t a strong pharmacometric argument be a strong rationale for approval?  In the case of the externally controlled superiority trial, 30 patients enrolled, receiving the new therapy (X-1 in our hypothetical case), where PK is performed, could provide evidence of response-exposure relationships and these could be placed in the context of the preclinical and phase 1 target attainment data available prior to the start of the “pivotal” trial. I agree with Paul – but would the regulatory authorities consider the more robust PK data substantial evidence in combination with everything else to allow approval? I’m not sure – but I think maybe the FDA is not sure either.

The EMA responded by again pointing out their tools including conditional approval with regular re-review of ongoing data for key products like X-1. Although this tool does not exist for the FDA per se, the FDA could approve a drug, require post-market studies and convene additional advisory committees or take other action based on emerging post-market data.

While the workshop was unable to establish a clear pathway forward for pathogen-specific antibiotics, it was clear that the usual pathways were going to be challenging to say the least.  It was also clear that post-approval data collection was going to be an essential piece of any approval for a pathogen-specific product for a Gram negative pathogen. And all of these considerations are now, thanks to the FDA, in the public domain.

Tuesday, July 19, 2016

FDA Workshop on Pathogen-Specific Antibiotic Development - Part 1

For the last two days, July 18-19, I was pleased to be able to attend a fascinating FDA Workshop on the development of antibiotics for use in a subset of patients with unmet needs. I am writing this blog while waiting for my very delayed flight from DC back home.

Unmet needs patients include, mostly, those with infections due to highly resistant pathogens where options for therapy are limited and/or where antibiotics for more usually resistant pathogens are not available in an oral formulation necessitating intravenous therapy. The subset of products specifically considered during this workshop is that targeting specific pathogens – e.g. an antibiotic active only against a single species of bacteria such as Pseudomonas aeruginosa or Acinetobacter baumanii. You can find all the slides used and other information here. I have blogged in the past regarding the FDA in particular and this thorny clinical development problem (1, 2, 3).

My impression in general is that, even if the FDA does not yet know what is the best approach to the development of pathogen-specific antibiotics, they wanted a public discussion of the issue to highlight both the need for these agents to be developed and the consequential need for a feasible pathway for their development.  They also wanted to be able to point to a public discussion of the extreme difficulty of designing and carrying out a standard trial with inferential statistics in this setting.  This public understanding would then make it just a little more comfortable for them to venture into heretofore unexplored territory in antibiotic development.

The meeting started with the usual general statements both from FDA and from EMA, the European regulatory agency. These were helpful and only emphasized the additional tools available in Europe for the approval of such agents compared to the US.  But, at least on day 1 of the meeting, the most important presentations, I thought, were the real life experiences of two companies attempting such trials. There were questions on the rationale for designing and carrying out the trials - I will review this below.

Example 1 – the CARE trial by Achaogen – presented by Ian Friedland. Achaogen is developing a new aminoglycoside antibiotic with activity against resistant pathogens called Plazomicin. Their original plan was to carry out a randomized superiority trial in infections caused by highly resistant pathogens –a noble but ultimately doomed endeavor. The original design called for the study of bloodstream infection and nosocomial pneumonia caused by carbapenem-resistant Gram negative pathogens. The endpoint was all cause mortality at day 28 (because the FDA requires this for non-inferiority nosocomial pneumonia trials?). The plan called for a 1:1 randomization between plazomicin + meropenem or tigecycline vs. colistin + meropenem or tigecycline calling for the enrollment of 360 evaluable patients (assumed 80% evaluability). Note the use of combination therapy – thought to be essential in these desperately ill patients with complicated infections. The trial initially screened 694 patients to enroll 14. Screening failures were caused by the lack of a carbapenem-resistant pathogen or the presence of more than 72 hours of previous antibiotic therapy (excluded by protocol) in these very sick patients in intensive care units (no surprise to most of us here).  The company quickly decided to carry out a standard, non-inferiority trial in urinary tract infection and altered their CARE trial design to be more accommodating to enrollment. Having started the original trial in early 2014, they project an enrollment of 100 patients by the end of this year – still far from their original goal of 360 patients. Enrollment appears to be speeding up slightly after their study amendments – but not enough to make this trial feasible as a stand-alone pivotal study for registration under today’s FDA standards. At this point the company plans to use the data in this smaller number of patients to support an application for approval based on the urinary tract infection trial data.

Example 2 – TANGO trials of meropenem plus a new beta-lactamase inhibitor, vaborbactam, from the Medicines Company presented by Mike Dudley. TANGO I was a standard, non-inferiority trial in urinary tract infection and the top line data has already been presented. They actually showed superiority (just) over their comparator, piperacillin-tazobactam.  Would meropenem have done the same without vaborbactam? One must ask . . . 

The company also is carrying out a TANGO 2 trial of meropnem-vaborbactam vs. best available therapy in urinary tract infection, intra-abdominal infection, nosocomial pneumonia and bacteremia suspected to be caused by carbapenem- resistant Gram negative pathogens. The trial is a comparative superiority trial with a 2:1 randomization. To support the control data for their trial, they carried out a retrospective study to gather data on the efficacy of best available therapy in regions where they would carry out the prospective clinical trial. The results of this retrospective study were surprising in that the patients were very sick and the mortality rates were high with a surprising 18% 28 day all cause mortality rate in patients with urinary tract infection. They also discovered an astounding 69 different best available therapy regimes in the different centers studied and they noted that combination therapy seemed not to improve outcome over monotherapy. They amended their trial protocol based on the findings of their retrospective study. They note that this trial will probably not yield inferential data.

Paul Ambrose raised the following question. If we can’t do inferential studies in these so-called pathogen specific indications, why don’t we just rely on PK/PD data to show that therapy is feasible and likely to be efficacious? While scientifically, one can’t argue with this position, the retort from companies is that physicians want to see actual clinical data in the patient population they will treat.  But does non-inferential data count? Can we not, rather, educate physicians to understand the importance of scientific basis of the PK/PD argument?

Day 2 was even more interesting.  Hold on to your hats!