Chapter 17 — Exercises
Items marked † have worked solutions in Appendix M.
A note before you begin. Several of these ask you to argue for positions you may not hold — including the strongest case for a compound this chapter rates ❌. That is deliberate and it is the most important work in the set. An evaluation you cannot state the opposing case for is not an evaluation.
A. Recall
17.1 State BPC-157's length, sequence, and approximate molecular weight, and name the structural feature that appears four times in fifteen residues.
17.2 † Write, in one sentence, the state of the human evidence for BPC-157 as of this chapter's writing. Then write the date next to it and explain why the date is part of the claim.
17.3 What does it tell you that BPC-157 has never been assigned a generic drug name? State explicitly both what this is evidence of and what it is not evidence of.
17.4 Name the four model families in the BPC-157 animal literature and give the typical injury or insult used in each.
17.5 † List Chapter 5's five reasons animal results fail to transfer to humans, and state which one is least discussed and why that matters for this compound in particular.
17.6 What is the difference between a compound's stability and its bioavailability? Give one sentence for each and one sentence on why the distinction matters.
B. The molecule, the name, and the mechanism
17.7 Read GEPPPGKPADDAGLV using Chapter 1 §1.2 only. Identify (a) the residues that make part of the chain rigid, (b) the residues that provide flexibility, (c) the net charge at physiological pH, and (d) the residue that would serve as a chemical attachment handle.
17.8 † No receptor has been definitively established for BPC-157. Explain what that means for the mechanism entry in a dossier — write the entry you would actually put in Field 3 — and explain why "acts on nitric oxide pathways" is not the right entry.
17.9 Chapter 5's rule 3 says never upgrade a rating with mechanism. Explain why that rule holds even for compounds whose mechanism is completely understood, and then explain the additional reason it holds with extra force here.
17.10 BPC-157 carries net negative charge and is roughly 1,419 daltons. From those two facts alone, what would you predict about its ability to cross cell membranes, and what would you predict about its default route of administration?
17.11 A compound is described as "derived from a sequence identified in human gastric juice." State three distinct things that description does not establish. Be precise; vagueness here is the whole exercise.
C. Reading the animal literature
17.12 Case Study 1's composite study measured load-to-failure and a histological score. Explain what each is a proxy for, and name the human outcome that neither can measure.
17.13 † The difference between treated and control animals was larger at day 14 than at day 28. Give the two interpretations this permits and explain how you would design a follow-up experiment to distinguish them.
17.14 Explain, in terms a non-scientist would follow, why blinding the person who scores an outcome is not the same as blinding the person who administers the treatment, and why both matter.
17.15 A review paper summarizes forty animal studies and concludes that BPC-157 "demonstrates efficacy across multiple injury models." A second source cites the review. Trace what has happened to the claim by the third citation, and identify the exact word whose loss does the damage.
17.16 † Explain why the number of published animal studies on a compound is not interpretable without a denominator, and why preclinical research has no denominator. Then state what kind of additional study would carry unusually high information value in a literature like this one, and why requesting it is not an accusation.
17.17 Someone argues that the consistency of results across four different tissue systems is strong evidence of a real effect. State the strongest version of their argument, then state the alternative explanation §17.5 offers, and say what evidence would distinguish the two.
D. The translation gap
17.18 † A rodent study reports an effect at a stated dose in milligrams per kilogram. Give three distinct reasons that figure cannot be converted into a human dose, and one reason specific to BPC-157 that makes the conversion even less reliable than usual.
17.19 Construct a table comparing a surgically transected rat Achilles tendon with a human chronic mid-portion Achilles tendinopathy across at least six dimensions. Then answer the question the table poses: are these the same disease at different scales, or different diseases?
17.20 §17.7 raises the possibility that a mechanism which sounds unambiguously beneficial — promoting new blood vessel growth — might have an ambiguous sign in a disease that already features abnormal neovascularization. Explain the concern, then explain why it is presented as a question rather than as a warning.
17.21 Roughly nine in ten compounds that enter human trials never reach approval, and those are compounds that had already cleared preclinical work. Explain what this base rate implies about how much a positive animal result should shift your confidence that a compound works in humans. Then explain why this is not an argument against doing animal research.
17.22 A person with a six-month shoulder problem starts using a compound, and the shoulder improves over eight weeks. List every explanation for that improvement other than the compound. Then say what the person could have done differently to make their own experience informative — and whether any such design is actually available to an individual.
17.23 Explain why "the trial hasn't been run for funding reasons, not scientific ones" is a true statement that does not change an evidence rating. Your answer must not rely on doubting the premise.
E. Route, stability, and the oral claim
17.24 † Name the five barriers between a swallowed peptide and the bloodstream, and state which one a stability argument addresses and which one it cannot touch.
17.25 BPC-157's proline-rich structure has been argued to confer unusual protease resistance. Explain why that argument is chemically reasonable, and then explain precisely why establishing it would still leave the oral efficacy claim unsupported.
17.26 Write the three-part question a seller of an oral peptide product owes an answer to. Then write what an acceptable answer looks like, using oral semaglutide as the model of a claim that has actually been substantiated.
17.27 A study reports that a peptide given by mouth protected the gastric mucosa of rats. Explain why this result is fully compatible with the compound having zero systemic bioavailability, and why that distinction is decisive for anyone hoping to treat a tendon.
17.28 A product is offered in a different salt form, described as more stable. Explain what a salt form can and cannot change about an oral peptide's prospects, in terms of the five barriers.
F. Evaluate this claim
Each item below is a paraphrased composite — a claim of a type that circulates widely, rewritten so that it belongs to no particular person or seller. For each: identify what is true in it, identify precisely where it fails, and write a two-sentence replacement that is accurate and that the original speaker could read without feeling insulted.
17.29 † "There are hundreds of peer-reviewed studies on this compound going back decades. Calling it unproven is just ignorance of the literature."
17.30 "It comes from gastric juice, so it obviously survives the stomach. That's why the oral version works and you don't need needles."
17.31 † "Thousands of people have used it for years and there are no reports of serious side effects. That's a better safety record than most prescription drugs."
17.32 "There's no evidence it works. It's rat science being sold to gym bros, and anyone taking it is wasting their money."
17.33 "Big pharma will never study it because they can't patent it. The fact that there are no human trials actually proves it works — if it didn't, they'd have funded a trial to kill it."
17.34 † "A registered clinical trial exists — I found it on ClinicalTrials.gov. So the human research is happening; it's just not published yet."
G. Writing the honest ❌
17.35 † Write a complete four-line evidence rating (claim, rating, reason, falsifier) for BPC-157 for gastrointestinal protection in humans, without copying §17.6's. Then explain, in two sentences, what makes this rating's reasoning different from the tendon rating's despite both being ❌ — and connect your answer to Chapter 5's rule 6.
17.36 † Choose a compound in your own dossier that you currently rate ❌ and that you wanted to work. Apply the six moves from §17.10's dossier procedure in full. Then apply them to a compound you have no feelings about, and compare the two entries side by side. Write one paragraph on what the comparison revealed about your own bias — specifically, whether move 1 (state the strongest true case for) was harder for one than the other, and in which direction. Date it; Chapter 40 comes back for it.