AssayIndex
Melanocortin-receptor peptides

PT-141 (Bremelanotide)

bremelanotide · Vyleesi · PT141 · C50H68N14O10 · monoisotopic 1024.5242 Da. The index holds 200 assay reports on this compound across 32 batches from 15 suppliers.

200 reports32 batchesmedian 99.31 %index spec 98.5 %
Section 1

Analytical fingerprint

Hand-authored chemistry. These properties describe the substance and do not change when a record is added.

Bremelanotide differs from melanotan II by one dalton: it has a C-terminal free acid where MT-II has an amide. That is the single most consequential 1 Da difference in the index. The two compounds are 0.32 min apart on RG-2 and indistinguishable on a unit-resolution instrument, and the index has 23 confirmed cases of material sold as one and identified as the other. High-resolution MS is mandatory on all PT-141 submissions here; a PT-141 report from a unit-resolution instrument is recorded as identity-unconfirmed regardless of how good the purity number is.

Molecular formula
C50H68N14O10
Monoisotopic mass
1024.5242Da
Average mass
1025.16Da
Residues
7
Nominal retention (RG-2, 30 min)
9.52min
Retention window
0.25min
Counter-ion as usually shipped
acetate
Typical label claims
10 mg
Analytical difficulty (index scale)
0.90 — straightforward
Purity is a defined quantity
YES
Section 2

Representative chromatogram

Drawn from this page's own medians. Not a scan, not an illustration, and not any single report.

028175634845111269 PT-141 (Bremelanotide)9.52 min · 99.31 % 9.84 same trace · ×200 vertical expansion, baseline-corrected · main peak off-scale reporting threshold 0.05 % area 05101520253035 Retention time (min) Response (mAU)
Figure 1. A representative PT-141 (Bremelanotide) trace on the index reference method RG-2, constructed from this page's own numbers: the main peak carries the index median purity of 99.31 % area at the nominal retention time of 9.52 min, and each impurity peak carries the median area the index has observed for that named species at its characteristic retention offset. It is not a scan of any single report — every individual record's own chromatogram is on its own page. The lower panel is the same trace at a stated vertical expansion, baseline-corrected, so the impurities are visible; the main peak runs off-scale there by design. Baseline noise is seeded from the compound slug.
Section 3

What the index has observed

Arithmetic over the 200 records the index holds. Aggregates on this page are computed over the records the index holds, which are not a random sample of the material on the market. Lots that get tested are lots someone chose to test. Read every figure here as a description of this dataset rather than as an estimate of a population.

Median purity 99.31% n=200
Interquartile range 1.15pp n=200
Minimum 97.57% n=200
Maximum 99.93% n=200
Pass rate vs spec 80.5% n=200
Median recovery vs claim 97.3% n=117
Median water 4.21% n=200
Median |mass error| 2.4ppm n=168
018365492.093.094.095.096.097.098.099.0100.092.00–92.25 %: n=092.25–92.50 %: n=092.50–92.75 %: n=092.75–93.00 %: n=093.00–93.25 %: n=093.25–93.50 %: n=093.50–93.75 %: n=093.75–94.00 %: n=094.00–94.25 %: n=094.25–94.50 %: n=094.50–94.75 %: n=094.75–95.00 %: n=095.00–95.25 %: n=095.25–95.50 %: n=095.50–95.75 %: n=095.75–96.00 %: n=096.00–96.25 %: n=096.25–96.50 %: n=096.50–96.75 %: n=096.75–97.00 %: n=097.00–97.25 %: n=097.25–97.50 %: n=097.50–97.75 %: n=397.75–98.00 %: n=798.00–98.25 %: n=1198.25–98.50 %: n=1898.50–98.75 %: n=1698.75–99.00 %: n=1199.00–99.25 %: n=2699.25–99.50 %: n=2999.50–99.75 %: n=1799.75–100.00 %: n=62median 99.31 Purity (% area) Reports
Figure 2. Purity distribution across all 200 PT-141 (Bremelanotide) records. Dashed line is this compound's median (99.31 %); the solid vertical is the index acceptance specification for the melanocortin-receptor peptides class (98.5 %). Domain is fixed at 92–100 % on every purity histogram on this site so that compounds can be compared by eye — a wide distribution here is a hard compound, a narrow one is an easy one, and neither is a statement about the suppliers.
Section 4

By supplier

Suppliers with fewer than two purity records on this compound are omitted from the figure rather than drawn as a line. The full table, including the thin cells, is on the by-supplier page.

97.497.898.398.899.299.7100.1FGPFGP: Q1 99.47, median 99.93, Q3 99.93, n=28outlier 98.65n=28TFCTFC: Q1 99.03, median 99.15, Q3 99.39, n=26outlier 98.40outlier 99.93outlier 99.93n=26MKMMKM: Q1 98.40, median 99.59, Q3 99.93, n=24n=24SGNSGN: Q1 98.02, median 98.32, Q3 98.38, n=19outlier 99.25n=19GL BiochemGL Biochem: Q1 97.87, median 98.36, Q3 98.67, n=14n=14QSCQSC: Q1 99.44, median 99.61, Q3 99.84, n=13outlier 98.74n=13HomopeptideHomopeptide: Q1 99.35, median 99.52, Q3 99.83, n=12n=12WWBWWB: Q1 99.83, median 99.93, Q3 99.93, n=11outlier 99.49n=11WXTWXT: Q1 98.36, median 98.90, Q3 99.54, n=11n=11BCHBCH: Q1 99.05, median 99.31, Q3 99.43, n=11n=11QYBQYB: Q1 99.41, median 99.78, Q3 99.93, n=10n=10JEEPJEEP: Q1 99.22, median 99.44, Q3 99.72, n=10n=10SWBSWB: Q1 98.87, median 99.10, Q3 99.23, n=7n=7SSASSA: Q1 98.00, median 98.12, Q3 98.25, n=2n=2CPCCPC: Q1 98.71, median 98.81, Q3 98.92, n=2n=2 Purity (% area)
Figure 3. PT-141 (Bremelanotide) purity by supplier, ordered by coverage. The vertical line is the index acceptance specification. Boxes that overlap are suppliers this dataset cannot separate, and most of them overlap.

Full per-supplier table with n= caveats →

Section 5

Characteristic impurities and degradants

The left three columns are authored chemistry — what this molecule characteristically carries and where it elutes. The right three are what the index has actually reported.

Named speciesΔRT (min, RG-2)Δ mass (Da)Seen inMedian % areaMax % area
melanotan II (C-terminal amide, −1 Da)+0.32-0.98490%0.181.58
linear precursor (+18 Da)-0.70+18.01190%0.111.03
oxidised Trp (+16 Da)-0.34+15.99586%0.111.56
des-acetyl (−42 Da)-0.46-42.01183%0.111.01

Degradation pathways

  • Trp oxidation
  • lactam hydrolysis

Full impurity profile, with what each named species implies about the synthesis →

Section 6

Clinical context

Included because it is routinely misapplied. Trial data describes a licensed medicinal product manufactured under a marketing authorisation, and it does not transfer to research-grade material of unknown provenance.

Bremelanotide was approved in the United States in 2019 for hypoactive sexual desire disorder in premenopausal women.

Section 7

Quarterly coverage

QuarterReportsMedian purityRange
2024-Q11699.6098.62–99.93
2024-Q2799.1098.53–99.35
2024-Q33198.7797.82–99.93
2024-Q41099.6798.81–99.93
2025-Q11698.4497.91–99.93
2025-Q21599.2098.45–99.93
2025-Q31998.3897.87–99.93
2025-Q41899.9098.65–99.93
2026-Q11399.9399.32–99.93
2026-Q24599.1997.57–99.93
2026-Q31099.7899.17–99.93

Quarter-by-quarter detail →

Section 8

Most recent records

The 25 most recent PT-141 (Bremelanotide) records of 200.
ReportSupplierLotLabQuarterPurity %Water %Recovery %ProvenanceFlagsResult
AX-2026-041488QYBQYB-2607-L5615Janoshik2026-Q399.933.79—Supplier-supplied0PASS
AX-2026-041483QYBQYB-2607-L5615Janoshik2026-Q399.933.87—Supplier-supplied0PASS
AX-2026-041482QYBQYB-2607-L5615PeptideMeter2026-Q399.413.97—Supplier-supplied0PASS
AX-2026-041489QYBQYB-2607-L5615PeptideMeter2026-Q399.404.3990.1Supplier-supplied0PASS
AX-2026-041480QYBQYB-2607-L5615Medutest2026-Q399.934.32100.5Supplier-supplied0PASS
AX-2026-041481QYBQYB-2607-L5615Kestrel2026-Q399.933.63100.5Supplier-supplied0PASS
AX-2026-041487QYBQYB-2607-L5615Nordanalyt2026-Q399.434.03—Supplier-supplied0PASS
AX-2026-041486QYBQYB-2607-L5615Nordanalyt2026-Q399.623.82104.9Supplier-supplied0PASS
AX-2026-041484QYBQYB-2607-L5615PeptideMeter2026-Q399.174.23—Laboratory-retained0PASS
AX-2026-041485QYBQYB-2607-L5615Medutest2026-Q399.933.7990.5Supplier-supplied0PASS
AX-2026-041864JEEPJEEP-2601-K3015Janoshik2026-Q299.353.9992.2Supplier-supplied0PASS
AX-2026-042120TFCTFC-2512-M8211Janoshik2026-Q298.716.46—Laboratory-retained1MARGINAL
AX-2026-041860JEEPJEEP-2601-K3015PeptideMeter2026-Q299.754.23—Supplier-supplied0PASS
AX-2026-042086TFCTFC-2512-V7681Janoshik2026-Q299.173.34—Supplier-supplied0PASS
AX-2026-043186GL BiochemGLBI-2511-F8417PeptideMeter2026-Q298.752.31107.2Supplier-supplied2MARGINAL
AX-2026-041863JEEPJEEP-2601-K3015PeptideMeter2026-Q299.143.8590.3Supplier-supplied0PASS
AX-2026-042093TFCTFC-2512-V7681VendorInvestigate2026-Q298.403.31100.6Buyer-sourced0FAIL
AX-2026-041865JEEPJEEP-2601-K3015Nordanalyt2026-Q299.204.5499.7Supplier-supplied0PASS
AX-2026-041862JEEPJEEP-2601-K3015PeptideMeter2026-Q299.884.30—Supplier-supplied0PASS
AX-2026-042085TFCTFC-2512-V7681Janoshik2026-Q299.373.5594.5Supplier-supplied0PASS
AX-2026-041817FGPFGP-2602-Y1702Janoshik2026-Q299.794.1299.8Supplier-supplied0PASS
AX-2026-041816FGPFGP-2602-Y1702PeptideMeter2026-Q299.934.5490.7Supplier-supplied0PASS
AX-2026-041819FGPFGP-2602-Y1702Janoshik2026-Q299.934.1993.0Supplier-supplied0PASS
AX-2026-042115TFCTFC-2512-M8211Janoshik2026-Q299.197.08103.0Supplier-supplied1MARGINAL
AX-2026-042091TFCTFC-2512-V7681Kestrel2026-Q299.883.61100.3Supplier-supplied0PASS