Paxos is a regulated financial company specializing in providing blockchain trust and custodial services for their clients. Paxos' settlement platform (Bankchain) is designed to be integrated with existing systems and to eliminate settlement risk in the exchange of digital assets. The company created a USD backed stablecoin called PAX, that is built on the Ethereum blockchain, and is meant to assist their clients in converting a variety of assets into digital versions, that can be more easily exchanged on a blockchain.

TrueUSD is a stablecoin backed by USD. It was created by TrustToken, a company that specializes in creating asset-backed tokens on the Ethereum blockchain. TrueUSD is fully collateralized and is transparently verified by third-party attestations.
TrueUSD was created within a legal framework that enables users to exchange USD directly with an escrow account. The platform is powered by smart contracts that ensure a 1:1 parity between USD and TrueUSD. Escrow accounts and regulatory compliance practices enable auditing and more legal protection for token holders.
Users wire funds to these third-party escrow accounts, and an equivalent amount of TUSD is generated to their ethereum addresses. Each TUSD can be redeemed for one US Dollar, that is held in escrow.

USD Coin is a stablecoin created by Coinbase and Circle. It's backed by USD (1 USDC=$1 USD), and is designed to be a stable digital currency that will fit within the trust and regulatory frameworks of the financial system, while still benefiting from the transparency and advantages of crypto powered networks. USDC is issued using the CENTRE open source framework and membership scheme, and it is available as a framework that multiple companies can leverage. Eventually other financial institutions will be able to become USDC issuers (and issuers of other fiat stablecoins - e.g. EURC, JPYC, GBPC), and customers will be able to tokenize USD and redeem USDC tokens in an open and interoperable ecosystem of financial institutions. A membership governance model for issuers will ensure that they meet technical, operational, regulatory, compliance and audit requirements.