Modified GRF 1-29 (CJC-1295 without DAC, Mod GRF 1-29)

Modified GRF 1-29 is the no-DAC variant of CJC-1295 — the same modified GHRH(1-29) sequence used to stimulate pituitary GH release through the GHRH receptor, but without the half-life-extending albumin-binding group.^[1]

Modified GRF 1-29 (Mod GRF 1-29) is the same 30-amino-acid GHRH analog sequence as CJC-1295 — including the four amino-acid substitutions that improve protease resistance — but without the maleimidopropionic acid linker that gives CJC-1295 with DAC its multi-day plasma half-life.

Within the peptide-research community, the two are often discussed as functionally distinct compounds despite their shared molecular core: 'CJC-1295' often defaults to the with-DAC form, while 'Modified GRF 1-29' or 'Mod GRF' refers specifically to the no-DAC form. The pharmacokinetic difference shapes how each is used.

Binds the GHRH receptor on anterior pituitary somatotrophs and triggers a discrete pulse of GH release. The short half-life means each dose produces a single physiologic-style pulse rather than sustained tonic elevation. When stacked with a ghrelin-mimetic GH secretagogue like ipamorelin (acting on GHSR-1a), the two pathways produce synergistic GH release — the most-discussed rationale for the classic 'CJC + Ipamorelin' stack.

Half-life of approximately 30 minutes — short enough that subcutaneous injection produces a discrete GH pulse rather than the multi-day tonic elevation seen with the DAC-linked form. This makes sleep-onset dosing the typical pattern, mimicking the natural nighttime GH pulse.

The peer-reviewed literature on Modified GRF 1-29 is summarized below across two tiers: human research (the highest standard), and preclinical / emerging research (animal models and early-stage human work).

This table summarizes commonly discussed claims and how the published evidence weighs in. The aim is clarity — supported claims, claims that look promising but need more data, and claims that outrun the science.

Subcutaneous injection at bedtime is the typical research-peptide pattern, often paired with ipamorelin to amplify the GH pulse. Dosing protocols vary widely. This describes research practice only.

Modified GRF 1-29 is the pharmacology-aware version of CJC-1295: same active sequence, intentionally dosed for pulsatile rather than continuous GH release. The mechanistic argument for pulsatile dosing — preserved feedback regulation, more physiologic profile — is reasonable. The clinical outcome data is limited. For users following the GHRH-analog literature, the pulsatile-versus-tonic distinction between Mod GRF 1-29 and CJC-1295-with-DAC is one of the more interesting open questions about how GH/IGF-1 elevation actually translates into outcomes.