PeptideStack
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Unanswered questions

Questions with no answer at all. Not questions with no accepted answer — those are elsewhere.

741 questions · page 18 of 31

11 votes0 answers10k views
Is minus 20 °C an acceptable storage condition for lyophilised survodutide?

The specifics, since they change the answer: minus 20 °C · survodutide. Somebody stated this to me confidently and I would like to check it before repeating it. I…

storage
storage

Storage conditions and their evidence base: minus twenty degrees for powder, refrigerated for solution, protection from light, and what the…

646 questions
peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
shelf-life
shelf-life

How long a preparation remains within specification: labelled expiry for a sealed lyophilised vial, beyond-use dating after reconstitution, and…

301 questions
asked by tare_weight 47k · 15 months ago
5 votes0 answers4.8k views
Does surface adsorption to the vial wall lose measurable peptide?

I have the same lot stored correctly as a comparator, if a side-by-side test would help. I have worked this out and I would like someone to find the error, because I…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
content-assay
content-assay

Quantified content: how many milligrams of peptide are actually in the vial, measured against a calibrated reference standard. A separate test…

438 questions
storage
storage

Storage conditions and their evidence base: minus twenty degrees for powder, refrigerated for solution, protection from light, and what the…

646 questions
asked by Dr_Idris_Coulibaly 40k · 15 months ago
16 votes0 answers11k views
Does reconstituting orforglipron with phosphate-buffered diluent change anything I should know about?

What I am working with: orforglipron · phosphate-buffered diluent. I keep seeing this stated as a fact with no explanation attached, and unexplained facts make me…

reconstitution
reconstitution

Taking a lyophilised vial to a solution of known concentration: choice of diluent, volume selection, how to add liquid without shearing the cake,…

330 questions
bacteriostatic-water
bacteriostatic-water

Water for injection containing roughly 0.9 per cent benzyl alcohol as a bacteriostatic agent. It suppresses growth in a multiple-withdrawal vial;…

112 questions
peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
asked by cake_intact 18k · 15 months ago
13 votes0 answers4.3k views
Does receptor desensitisation explain the plateau?

I would like to know how much of this is established and how much is a reasonable story. I understand the observation; what I do not understand is the mechanism…

glp1-mechanism
glp1-mechanism

Receptor-level pharmacology: GLP-1R as a class B GPCR, cAMP and PKA signalling, biased agonism, internalisation and resensitisation, and the…

175 questions
plateau
plateau

A stall in progress: distinguishing adaptive thermogenesis from measurement error from adherence drift, how long to observe before changing…

35 questions
dose-escalation
dose-escalation

The decision to move up a step: what evidence supports a four-week interval, what happens when you compress it, and how trial protocols handled…

88 questions
asked by valentina_rossi 16k · 16 months ago
18 votes0 answers10k views
Is SURMOUNT-1 a fair comparison of a GLP-1 receptor agonist against its comparator arm?

Setup, so nobody has to ask: SURMOUNT-1 · a GLP-1 receptor agonist. This has the shape of a fact but I cannot find its origin. What I found instead were three…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
semaglutide
semaglutide

A GLP-1 receptor agonist with a fatty-acid-acylated backbone and a roughly one-week half-life, marketed for type 2 diabetes and for weight…

360 questions
tirzepatide
tirzepatide

A dual GIP and GLP-1 receptor agonist. Questions here cover the SURPASS and SURMOUNT programmes, the practical differences from a pure GLP-1…

162 questions
asked by cake_collapsed 13k · 16 months ago
16 votes0 answers7.4k views
Has anyone independently verified an FGP mazdutide batch COA?

Stated plainly: FGP · mazdutide. This has the shape of a fact but I cannot find its origin. What I found instead were three secondary sources all citing each other.…

vendor-vetting
vendor-vetting

Evaluating a supplier on evidence rather than reputation: testing history across batches, whether certificates are batch-specific, how failures…

436 questions
coa
coa

Certificates of analysis: what fields a useful one carries, how to tell a real analytical report from a marketing document, batch and lot…

749 questions
batch-testing
batch-testing

Testing at the batch or lot level: sampling plans, how many vials from a lot need testing to say anything about the lot, and the difference…

865 questions
asked by Dr_Jonas_Halvorsen 41k · 16 months ago
16 votes0 answers4.6k views
Is 1 mg/mL a sensible working concentration for liraglutide, or should I go lower?

The case in front of me: 1 mg/mL · liraglutide. I would like the axes of comparison first and the recommendation second. I have tried the first option and it works;…

diluent-volume
diluent-volume

Choosing how much diluent to add, which is really a question about what you want your measurement resolution to be. Larger volumes buy you…

308 questions
reconstitution
reconstitution

Taking a lyophilised vial to a solution of known concentration: choice of diluent, volume selection, how to add liquid without shearing the cake,…

330 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
asked by hana_petrikova 19k · 16 months ago
3 votes0 answers2.3k views
Is there any published stability data for tirzepatide at 40 °C?

The specifics, since they change the answer: tirzepatide · 40 °C. Somebody stated this to me confidently and I would like to check it before repeating it. I would…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
storage
storage

Storage conditions and their evidence base: minus twenty degrees for powder, refrigerated for solution, protection from light, and what the…

646 questions
clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
asked by ellis_thorne 17k · 16 months ago
30 votes0 answers12k views
Does holding at 60 mg for two weeks before escalating reduce headache?

What I am working with: 60 mg · two weeks · headache. I keep seeing this stated as a fact with no explanation attached, and unexplained facts make me suspicious. My…

titration
titration

Stepwise dose increases over weeks, why the label schedules exist at all, and what tolerability-driven deviation from a schedule looks like in…

444 questions
nausea
nausea

The dominant tolerability signal in every trial of the class: incidence, timing relative to a dose step, duration, and the distinction between…

346 questions
dose-escalation
dose-escalation

The decision to move up a step: what evidence supports a four-week interval, what happens when you compress it, and how trial protocols handled…

88 questions
asked by thermal_mass 16k · 16 months ago
21 votes0 answers16k views
What is the pharmacokinetic argument against splitting a weekly dose?

This is the third vial from the same lot, so I can compare against two known-good ones. I suspect the usual explanation for this is wrong, or at least incomplete. I…

split-dosing
split-dosing

Dividing a weekly dose across more than one administration. Questions here concern the pharmacokinetic rationale, whether the peak-to-trough ratio…

39 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
glp1-mechanism
glp1-mechanism

Receptor-level pharmacology: GLP-1R as a class B GPCR, cAMP and PKA signalling, biased agonism, internalisation and resensitisation, and the…

175 questions
asked by ellis_thorne 17k · 16 months ago
7 votes0 answers2.8k views
What does SOUL tell me about vomiting at the 2.5 mg dose?

Stated plainly: SOUL · vomiting · 2.5 mg. I have read the primary source rather than the summary, which has left me with more questions. I understand the headline. I…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
gi-side-effects
gi-side-effects

The gastrointestinal cluster as a whole - nausea, vomiting, diarrhoea, constipation, reflux, early satiety - with trial incidence rates, dropout…

416 questions
titration
titration

Stepwise dose increases over weeks, why the label schedules exist at all, and what tolerability-driven deviation from a schedule looks like in…

444 questions
asked by bac_or_bust 37k · 16 months ago
26 votes0 answers13k views
Is hair shedding at month three telogen effluvium or something else?

It has now persisted for three weeks, which is what moved this from tolerable to worth asking about. I can parse the result. I am less sure what it licenses me to…

hair-loss
hair-loss

Telogen effluvium following rapid weight loss versus a drug-attributable effect: the timing signature that distinguishes them, protein and…

14 questions
nutrition
nutrition

Eating on a suppressed appetite: hitting nutritional targets inside a small energy budget, micronutrient risk, meal structure, and what the trial…

92 questions
protein-intake
protein-intake

Protein targets in grams per kilogram, per-meal distribution and the leucine threshold, and the evidence for a higher intake specifically during…

53 questions
asked by wren_calloway 14k · 16 months ago
15 votes0 answers11k views
Does splitting a 4 mg weekly dose of survodutide across two administrations change anything?

The particulars: 4 mg · survodutide. I would like the mechanism, because I want to be able to reason about the cases nobody has written about. I have tried to reason…

split-dosing
split-dosing

Dividing a weekly dose across more than one administration. Questions here concern the pharmacokinetic rationale, whether the peak-to-trough ratio…

39 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
glp1-mechanism
glp1-mechanism

Receptor-level pharmacology: GLP-1R as a class B GPCR, cAMP and PKA signalling, biased agonism, internalisation and resensitisation, and the…

175 questions
asked by birk_nordahl 20k · 16 months ago
12 votes0 answers6.2k views
Why did two Homopeptide lots of tirzepatide differ on content assay?

The case in front of me: Homopeptide · tirzepatide. I think I have a problem. I am not yet sure whether it is a real problem or a measurement artefact. I want to know…

batch-testing
batch-testing

Testing at the batch or lot level: sampling plans, how many vials from a lot need testing to say anything about the lot, and the difference…

865 questions
content-assay
content-assay

Quantified content: how many milligrams of peptide are actually in the vial, measured against a calibrated reference standard. A separate test…

438 questions
vendor-vetting
vendor-vetting

Evaluating a supplier on evidence rather than reputation: testing history across batches, whether certificates are batch-specific, how failures…

436 questions
asked by priya_menon 11k · 16 months ago
22 votes0 answers18k views
What does the mechanism of mazdutide predict that REDEFINE-1 did not test?

Details up front: mazdutide · REDEFINE-1. I can predict the outcome but I cannot explain it, which means I will get the next case wrong. I would like to know how…

glp1-mechanism
glp1-mechanism

Receptor-level pharmacology: GLP-1R as a class B GPCR, cAMP and PKA signalling, biased agonism, internalisation and resensitisation, and the…

175 questions
clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
gip-receptor
gip-receptor

GIP receptor pharmacology, and the still-unsettled question of whether agonism or antagonism at GIPR is the metabolically useful direction.…

83 questions
asked by fiadh_cronin 14k · 16 months ago
28 votes0 answers23k views
How long does a Hangzhou to Ireland lane usually take with tracking?

Details up front: Hangzhou · Ireland. I can parse the result. I am less sure what it licenses me to conclude. I have deliberately not looked at anyone else’s…

international-shipping
international-shipping

Cross-border movement of research material: transit lanes and their thermal profiles, tracked versus untracked, declaration accuracy, and what…

427 questions
customs
customs

Customs handling: how declarations are assessed, why a parcel sits at a facility for a week, seizure notices, and the practical difference between…

186 questions
cold-chain
cold-chain

Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…

524 questions
asked by sasha_ferreira 15k · 16 months ago
10 votes0 answers5.3k views
Is a TFC order from Wuxi likely to hold cold chain to Poland?

The case in front of me: TFC · Wuxi · Poland. The failure mode I am trying to avoid is making this decision emotionally. I have twelve months in view and I would like…

cold-chain
cold-chain

Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…

524 questions
international-shipping
international-shipping

Cross-border movement of research material: transit lanes and their thermal profiles, tracked versus untracked, declaration accuracy, and what…

427 questions
vendor-comparison
vendor-comparison

Side-by-side comparison of suppliers on measurable axes - independently confirmed purity and content, lead time, cold-chain handling,…

351 questions
asked by oona_kekkonen 16k · 16 months ago
34 votes0 answers19k views
Is there any published stability data for a GLP-1 receptor agonist at 2–8 °C?

What I have: a GLP-1 receptor agonist · 2–8 °C. I would rather be corrected now than propagate something wrong. I am specifically not interested in a testimonial; I…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
storage
storage

Storage conditions and their evidence base: minus twenty degrees for powder, refrigerated for solution, protection from light, and what the…

646 questions
clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
asked by kofi_mensah 12k · 16 months ago
30 votes0 answers15k views
Does albumin-to-creatinine ratio tell me anything about hepatic fat on dulaglutide?

Details up front: albumin-to-creatinine ratio · dulaglutide. I suspect the usual explanation for this is wrong, or at least incomplete. I am aware this may have a…

liver-enzymes
liver-enzymes

ALT, AST, GGT and ALP: what they do and do not indicate about hepatic fat, why enzymes are a poor surrogate for histology, and where non-invasive…

50 questions
mash
mash

Metabolic dysfunction-associated steatohepatitis: histological endpoints, resolution without worsening fibrosis, fibrosis improvement by stage,…

51 questions
bloodwork
bloodwork

Laboratory monitoring: which panels are worth ordering, sensible intervals, reference-range versus optimal-range arguments, and how to read a…

284 questions
asked by leonid_marchuk 15k · 16 months ago
22 votes0 answers11k views
What does REDEFINE-1 report at the 10 mg dose level?

Numbers first: REDEFINE-1 · 10 mg. This is presented as though it settles something, and I am not convinced it does. I have two documents that appear to disagree,…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
titration
titration

Stepwise dose increases over weeks, why the label schedules exist at all, and what tolerability-driven deviation from a schedule looks like in…

444 questions
asked by cal_hennessy 14k · 16 months ago
7 votes0 answers2.9k views
Is the maximum studied dose the same as the maximum useful dose?

My records go back to the first dose with dates, so I can reconstruct the timeline exactly. I suspect the honest answer is that it depends, in which case I would like…

maintenance-dose
maintenance-dose

Staying put: the lowest dose that holds a result, the difference between the maximum studied dose and the maximum useful dose, and what the…

44 questions
clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
dose-escalation
dose-escalation

The decision to move up a step: what evidence supports a four-week interval, what happens when you compress it, and how trial protocols handled…

88 questions
asked by eighty_six_hours 16k · 16 months ago
35 votes0 answers13k views
What would make you reject an ERP vial on visual inspection alone?

For context, I am working with a 10 mg presentation and a 2 mL fill. I am trying to build something sustainable rather than something thorough that I will abandon. I…

vial-inspection
vial-inspection

What you can learn by looking: cake morphology, meniscus films, fibres versus stopper fragments versus true particulates, clarity after…

66 questions
harm-reduction
harm-reduction

Reducing avoidable risk where a decision has already been made: independent verification before use, sterility practice, dose arithmetic checked…

445 questions
sterility
sterility

Sterility as a test result rather than an adjective. Covers what a sterility test actually measures, why "sterile filtered" on a document is close…

122 questions
asked by drawn_and_capped 15k · 16 months ago
14 votes0 answers15k views
What does a 98.4% purity with a sampling plan attached let me conclude?

Setup, so nobody has to ask: 98.4% · sampling plan. I would like help reading this properly rather than being told what conclusion to reach. I have the full report…

purity
purity

Purity as chromatographic area per cent - the fraction of detected material that is your target peak. It says nothing about how much material is…

788 questions
coa
coa

Certificates of analysis: what fields a useful one carries, how to tell a real analytical report from a marketing document, batch and lot…

749 questions
hplc
hplc

Reverse-phase high-performance liquid chromatography, the workhorse purity method. Column chemistry, mobile-phase choice, gradient slope,…

466 questions
asked by rukhsana_iqbal 14k · 17 months ago
37 votes0 answers38k views
What did the placebo arm of TRIUMPH-3 report for injection-site erythema?

What I am working with: TRIUMPH-3 · injection-site erythema. I would like help reading this properly rather than being told what conclusion to reach. I have the full…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
gi-side-effects
gi-side-effects

The gastrointestinal cluster as a whole - nausea, vomiting, diarrhoea, constipation, reflux, early satiety - with trial incidence rates, dropout…

416 questions
nausea
nausea

The dominant tolerability signal in every trial of the class: incidence, timing relative to a dose step, duration, and the distinction between…

346 questions
asked by cake_intact 18k · 17 months ago