Which CAS numbers are listed?

CAS 1016636-76-2 is a key palbociclib scaffold intermediate. CAS 571188-59-5 is a shared building block applicable to palbociclib and ribociclib routes.

Can we take only palbociclib, or only ribociclib?

Yes. The two molecules are scoped separately. The shared side-chain block can support either route; the scaffold intermediate is palbociclib-specific.

Can we take only intermediates, or only API?

Yes. The two layers are modular. Many partners start with the listed building blocks, then add API once coupling, regioisomers and residual starting materials are firm.

Who is this program for?

Marketing-authorisation holders, regional manufacturers and distributors who need qualified palbociclib or ribociclib intermediates or API. Not for patients or retail dispensing.

Palbociclib and ribociclib key intermediates and API

Oral CDK4/6 — take the listed building blocks, API, or both, for either molecule or both programs.

CDK4/6
Oral
Key intermediates
API

01Scaffold

Key intermediates

A palbociclib core scaffold plus a protected aminopyridyl-piperazine side chain shared with ribociclib.

CAS 1016636-76-2 and 571188-59-5 listed
Assay, regioisomers, residual starting materials and reaction-related impurities named in the spec

02Commercial

Active pharmaceutical ingredient

Palbociclib and ribociclib API for breast-cancer generic-development programs.

Coupling performance starts with the listed heterocyclic blocks
Downstream purification and manufacturing efficiency named in the program plan

Building blocks listed

A key palbociclib scaffold intermediate and a shared building block used on palbociclib and ribociclib routes. Tell us which numbers you need and the volume range.

1016636-76-2

571188-59-5

Originator programs — not Unibest branded products

CDK0/6

Oral inhibitors in breast cancer (originator brands: Ibrance, Kisqali)

Industry context

Palbociclib and ribociclib are commercially validated oral CDK4/6 inhibitors with established and expanding applications in breast cancer treatment. That is why a core heterocyclic scaffold, a shared side-chain building block and API need a commercial-ready supply — not a research-only catalogue.

For manufacturers and marketers

Marketing-authorisation holders

Regional manufacturers

Distributors

Not a consumer offer, and not originator-branded product.

Why this supply

The core scaffold and the protected side chain are listed separately, so generic API work can be scoped to the molecule and the step you are running.

Palbociclib scaffold intermediate

6-Bromo-2-chloro-8-cyclopentyl-5-methylpyrido[2,3-d]pyrimidin-7(8H)-one (CAS 1016636-76-2) is a key palbociclib scaffold intermediate.

Shared side-chain building block

tert-Butyl 4-(6-aminopyridin-3-yl)piperazine-1-carboxylate (CAS 571188-59-5) is a protected aminopyridyl-piperazine building block applicable to palbociclib and ribociclib routes.

Regioisomers and residual starting materials

Consistent control of assay, regioisomeric impurities, residual starting materials and reaction-related impurities can improve coupling performance.

Purification and manufacturing efficiency

That same control supports downstream purification and overall API manufacturing efficiency. We quote against specification and volume — not a list price on this page.

How a program starts

Same sequence whether you take listed building blocks, API, or both — and whether you start with one molecule or both.

01
Scope
Which molecule, which CAS numbers, grade, volume and whether you need intermediates, API, or both. We confirm what we can stand behind before work starts.
02
Align the file
Specification, CoA format, regioisomers, residual starting materials and reaction-related impurities — written down while gaps are still cheap to close.
03
Qualify supply
Listed lots and/or commercial API against that spec. Audit findings stay in the same program plan.
04
Deliver and hold
First shipment, then change control from one owner.

Frequently asked

No. This is a B2B supply of key intermediates and API for the molecules. It is not a consumer product and not offered under originator brand names, including Ibrance and Kisqali.

Ready to scope a supply?

Send the molecule, grade and a volume range. We reply with what we can stand behind.