Weekly Issue — 2025-08-31

Until recently, the question of how to move a patient from a pure GLP-1 receptor agonist — semaglutide, dulaglutide, liraglutide — onto tirzepatide, which hits both the GLP-1 and GIP receptors, was answered mostly by clinician instinct. The drugs are cousins, not twins. Tirzepatide's dual-agonist mechanism is meaningfully different, and there was no clean protocol for the handoff.

A 2024 retrospective case series out of a hospital pharmacy is one of the first published attempts to fill that gap. The authors followed 10 adults with type 2 diabetes who met internal criteria for switching from a GLP-1 RA to tirzepatide, and tracked A1C and weight at three and six months. The mean A1C change was −0.7% at 3 months and −1.4% at 6 months, with mean weight loss of 3.6 kg and 6 kg over the same windows. A third of the patients with six-month follow-up hit at least 10% body-weight reduction. Few adverse events were reported.

Read that paragraph again before you get excited. Ten patients. Retrospective. Open-label by definition. No control arm. The authors themselves frame it as hypothesis-generating — a signal that switching can be considered when A1C and weight goals aren't being met on a GLP-1 alone. That is a long way from a randomized trial telling you it's better.

Zoom out and the switching question is really a market question. Tirzepatide has become the dominant story in this class because the phase-3 program for type 2 diabetes and obesity put up numbers that older GLP-1s, on average, didn't match. As clinicians try to translate that into care, patients on dulaglutide or semaglutide are asking whether to move — and the case series above is, frankly, the only thing in the published record that even gestures at an answer for that specific transition.

Meanwhile, the back end of the GLP-1 market is doing something the supplement aisle has done for decades — fragmenting into branded and generic-equivalent options. That's where the second paper comes in.

In a multicenter, randomized, open-label, active-comparator phase-3 study, 440 Chinese adults with type 2 diabetes were randomized 1:1 to either LY05008 — a dulaglutide biosimilar — or the reference product dulaglutide (Trulicity), 1.5 mg subcutaneously once weekly for 24 weeks. The primary endpoint was change in HbA1c from baseline to week 24. The two arms landed essentially on top of each other: −1.44% for the biosimilar versus −1.41% for the reference product. Safety, pharmacokinetics, and immunogenicity were also assessed.

That's exactly what a biosimilar trial is supposed to show, and it's what every lifter who has ever sourced a generic version of a brand-name drug should pay attention to: when the regulatory machinery works, a well-run phase-3 study can demonstrate that a biosimilar performs in the same neighborhood as the originator. It does not mean every grey-market peptide labeled “dulaglutide” on the internet is the same molecule. It means one specific product, in one specific trial, met the bar.

If you're the kind of lifter who actually pulls up PubMed before changing your pre-workout, here's the honest framing. The switching evidence is a small, retrospective signal that tirzepatide can do additional work in patients who haven't reached their goals on an older GLP-1. The biosimilar evidence is a much more robust signal that the dulaglutide molecule, made by a different manufacturer to a regulated standard, can perform comparably to the originator over six months.

Neither of these is a green light for the gym-bro use case. Both studies were in people with type 2 diabetes, under clinical supervision, with structured monitoring of A1C, weight, and side effects. The relevant outcomes for a metabolically healthy 28-year-old chasing a leaner offseason — long-term lean-mass retention, training performance, recovery, endocrine effects over years — are not in these papers. They're not in most of the GLP-1 literature yet, full stop.

The class is moving fast. The data is moving slower. That gap is where hype lives, and where the people selling you something thrive. The smart move, as always, is to read the actual studies, talk to a clinician who knows your bloodwork, and let the evidence — not the algorithm — set the pace.

Here's the setup. GLP-1 receptor agonists — the class that includes the brand names you've seen in every group chat — aren't just a molecule in a bottle. They're a drug plus a delivery device, usually an injector pen. That combination matters, because in U.S. pharmaceutical law, the device is patentable too. So is the formulation. So is the dose schedule, the cartridge geometry, the button mechanism, the packaging. A legal scholar at Harvard, William Feldman, lays out in a recent peer-reviewed analysis how brand-name manufacturers stack dozens of these peripheral patents around a single product — a tactic the literature has nicknamed a "patent thicket."

A thicket doesn't have to win in court. It just has to be expensive and slow to cut through. Every patent is a potential lawsuit a generic challenger has to fight, and every fight is years and millions of dollars. The math gets ugly fast, and a lot of generic makers simply… don't bother.

The second move Feldman dissects is even slicker. It's called product hopping, and it works like this: right before a brand-name drug faces generic competition, the manufacturer rolls out a tweaked version — a new formulation, a new dose, a new device — with fresh patent protection. Doctors get nudged toward the new version. Insurers move coverage. By the time a generic of the original product finally arrives, the market has quietly migrated to a product the generic doesn't match. The Journal of Law, Medicine & Ethics analysis identifies inhalers as the textbook case — patients have been paying brand-name prices for asthma drugs whose active ingredients went off-patent ages ago — and warns that GLP-1s share the same drug-device structure that made inhalers so hop-able.

This is the part that should make any of us paying out of pocket sit up. It is not a conspiracy theory. It is a documented regulatory pattern, now being formally flagged in the legal literature as a near-term risk for the most in-demand drug class of the decade.

Here's the cautiously hopeful part. Feldman notes that during the last legislative session, the Senate Judiciary Committee advanced three bipartisan bills aimed at speeding up generic competition. Bipartisan. In this Congress. That alone tells you the patent-gamesmanship problem has become hard to ignore.

But the analysis is blunt that the bills, as written, are a step forward and not a fix. The author argues that real reform would also need: routine re-examination by the U.S. Patent and Trademark Office of the patents drugmakers list with the FDA; a bigger role for the FDA itself in vetting those listings; caps on how many patents a brand can throw at a generic challenger in a single lawsuit; stronger incentives for companies willing to mount challenges in the first place; and more flexibility for the FDA to approve complex generics — the drug-device combinations exactly like GLP-1 pens.

None of that is on the President's desk. Most of it isn't even in a bill yet. Which is why "regulatory concern" is the honest label here, not "regulatory crisis solved."

I want to be careful here, because this is the spot where health journalism likes to slide into either doom or hot tips. Neither is appropriate. The paper is a legal-policy analysis, not a clinical trial or a price forecast. It does not predict a specific date when GLP-1s will get cheaper, and it does not tell you what to do about your prescription. What it does do is name the structural reasons you shouldn't budget around a sudden generic-driven price drop in the next year or two.

If you're navigating perimenopause, metabolic shifts, or a GLP-1 conversation with your clinician right now, the practical read is this: treat affordability as a planning question, not a waiting game. Ask your prescriber about clinical alternatives, patient-assistance programs, and whether the dose or device you're being started on has known supply or coverage quirks. Bring the question of cost into the appointment out loud. None of that is medical advice from me — I'm a writer, not your doctor — but it is the kind of conversation the policy reality justifies.

The bigger picture worth holding onto: the GLP-1 story isn't only a story about a drug. It's a stress test of whether the U.S. patent system can handle a blockbuster fast enough for the people who actually need it to be affordable. Right now, the honest answer from the legal literature is not yet. Knowing that won't lower your copay this month. But it will keep you from being surprised — and from outsourcing your planning to a generic that may take longer to arrive than the headlines suggest.

NAD+ — nicotinamide adenine dinucleotide — is the redox workhorse that lets your mitochondria turn substrate into ATP and lets sirtuins and PARPs do their repair-and-signal business. Tissue NAD+ pools shrink with age, and NR is one of several precursors shown to refill them. That refill, in various rodent and small human studies, has been linked to improvements in markers of metabolic and immune function.

Here is the gap: most of those experiments measured NR in animals living quiet laboratory lives. Real organisms — and certainly the readers of a performance magazine — are not unstressed. Training load, sleep debt, work pressure, illness, and the slow grind of aging itself are chronic stressors. The question the new GeroScience study asks is disarmingly simple: when you add daily physiological stress on top of NR supplementation in aged animals, do the benefits hold?

On the hematology side, NR looked good. Chronic stress in aged mice tends to push platelet counts down — stress-induced thrombocytopenia — and six weeks of NR supplementation protected against that drop. The treated animals also showed higher frequencies of B and T cells, the adaptive immune system's two main lymphocyte lineages. Read narrowly, that is the kind of result the NAD+ field has been hoping to see: a precursor that keeps the immune compartment a little more resilient when the organism is being pushed.

For a writer who follows the performance-science beat, this is the part that is genuinely interesting. Aged immune systems drift toward a state sometimes called immunosenescence — fewer naive lymphocytes, more low-grade inflammation, slower responses to new antigens. Anything that nudges lymphocyte frequencies up in an aged, stressed animal is mechanistically worth a second look. The authors are careful, though, to frame this as a frequency shift in mice, not a demonstration of better infection outcomes.

Here is the wrinkle. The same supplementation regimen that protected platelets and shifted lymphocyte frequencies also, in the authors' words, heightened stress sensitivity, with increased anxiety-like behaviors in the treated animals. Cognitive performance, measured separately, did not change in either direction.

That is not the shape of result the supplement aisle is built to communicate. A clean longevity story wants the bars to all point the same way: more NAD+, better blood, calmer behavior, sharper mind. What the data actually delivered was a split — an immune-and-hematology arrow pointing one way and a behavioral arrow pointing the other. The authors call it a dual role, and the framing is appropriate: NR is doing something real in these animals, but "something real" is not synonymous with "uniformly good."

Mouse data is mouse data. Aged C57-style models under controlled stressors are not a stand-in for a 42-year-old marathoner stacking a build block on top of a demanding quarter at work. The cautious read is that this single paper does not overturn the broader NR literature; it adds a variable that has been largely missing from it.

The mechanistic question the paper opens — and does not answer — is whether bumping NAD+ pools in already-stressed tissue interacts with stress-response pathways in ways the unstressed studies could not see. NAD+ is a substrate for sirtuins and for the PARP family, both of which are themselves stress-responsive. It is at least biologically plausible that flooding that substrate pool while the hypothalamic-pituitary-adrenal axis is being repeatedly engaged produces different downstream effects than flooding it in a quiet cage. Plausible is not proven. It is, however, exactly the kind of question that a serious supplement category should be running toward, not past.

For an endurance reader, the practical implication is modest but real: the assumption that NR's benefits stack linearly on top of a high-stress training and life load is, at present, an assumption. The authors themselves recommend that future research on NR consider stress as a variable in order to optimize its therapeutic use in aging populations. That is a polite way of saying the existing human trials may have been answering an easier question than the one consumers are actually asking.

The NAD+ story is not collapsing. NR still has a coherent mechanistic rationale and a body of preclinical and early human data behind it. But the 2025 GeroScience paper is a useful corrective to a category that has, fairly or not, slid into a tone of quiet certainty. In aged mice under chronic stress, six weeks of NR produced a genuinely mixed picture: better in the blood, unchanged in the maze, worse in the open field. That is not a verdict. It is an invitation to study the molecule the way real users actually live — tired, pressured, and a long way from a quiet cage.

For a performance reader, the more interesting frontier is no longer "does NR raise NAD+?" — it does — but "under what conditions does raising NAD+ translate to the outcomes that matter?" On the evidence so far, stress is one of the conditions that belongs in the question.